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camcbride1987
If you change the engine load and RPMs the trims should change
If they do not then the PCM is not going into closed loop as it sees some sensor out of range
Above about 160F deg coolant and all is well, then PCM goes into closed loop
Using a OBD scanner monitor the engine loop PID and if not going to CL then monitor PIDs
to see what sensors like MAF, ECT, O2s report
When in OL, the PCM ignores those sensors, so the fuel trim cells do not get updated or active
If disconnecting battery just for a few seconds that flushes all PCM relearns and long averages
and when battery connected again means short time relearn values, so the fuel trims should often change
until enough average is obtained
If they do not then the PCM is not going into closed loop as it sees some sensor out of range
Above about 160F deg coolant and all is well, then PCM goes into closed loop
Using a OBD scanner monitor the engine loop PID and if not going to CL then monitor PIDs
to see what sensors like MAF, ECT, O2s report
When in OL, the PCM ignores those sensors, so the fuel trim cells do not get updated or active
If disconnecting battery just for a few seconds that flushes all PCM relearns and long averages
and when battery connected again means short time relearn values, so the fuel trims should often change
until enough average is obtained
Ok I understand PCM must not be going into CL.
I replaced the CRK sensor. Because of a P0017 and P0300 code. The old CRK sensor didn't ohm out. It was dead.
I replaced the coils,The spark plugs,fuel injectors and manifold gasket.while car was running rough I sprayed car cleaner around every boot, hose and base of manifold. And hose on back of manifold for brake booster. No rpm increases.
I also replaced all four cam sensors.
Now I read the crk when replaced. You need to do a relearn..I tried doing one on my Launch and it goes through the steps but at end it says not satisfied in red.
The ECT sensor showed 180°
So why the PCM is not going into CL I don't understand.
Car runs very rough but rpm idle is constant at 750 rpms. As I step on gas in park it smooths out a bit.
I seem to smell little raw fuel but nothing is leaking.
It's getting frustrating to say the least
Also when I check injectors I have to enable them and if I go back later I have to enable them again..
I don't understand why?
My launch shoes the PCM volts are good.like I said the P0017 and P0300 is what Im getting.
I can't do a crk relearn for some reason
I replaced the CRK sensor. Because of a P0017 and P0300 code. The old CRK sensor didn't ohm out. It was dead.
I replaced the coils,The spark plugs,fuel injectors and manifold gasket.while car was running rough I sprayed car cleaner around every boot, hose and base of manifold. And hose on back of manifold for brake booster. No rpm increases.
I also replaced all four cam sensors.
Now I read the crk when replaced. You need to do a relearn..I tried doing one on my Launch and it goes through the steps but at end it says not satisfied in red.
The ECT sensor showed 180°
So why the PCM is not going into CL I don't understand.
Car runs very rough but rpm idle is constant at 750 rpms. As I step on gas in park it smooths out a bit.
I seem to smell little raw fuel but nothing is leaking.
It's getting frustrating to say the least
Also when I check injectors I have to enable them and if I go back later I have to enable them again..
I don't understand why?
My launch shoes the PCM volts are good.like I said the P0017 and P0300 is what Im getting.
I can't do a crk relearn for some reason
Without CKP relearned, engine will not run correctly, including multi misfires (P0300) DTC
You sure the new CKP is the right one for your engine ?
Is it from a quality vendor ?
Cannot do a CKS relearn if ANY DTCs have tripped, so clear them before starting the CKP relearn
Did you do as I mentioned, is ECT sensor reporting correct coolant temp, must be over 160F deg
With scanner do other sensors like MAF, MAP, O2s values look normal
Cannot do CKP relearn during OL
Possible the scanner you're using is sending the CKP relearn command ?
Here are a couple of GM ways do to CKP relearn process, not sure if these are correct for your year/engine
Crankshaft Position System Variation Learn
Install a scan tool.
Monitor the engine control module (ECM) for DTCs with a scan tool.
If other DTCs are set, except DTC P0315, refer to Diagnostic Trouble Code (DTC) List - Vehicle for the applicable DTC that set.
Select the crankshaft position (CKP) variation learn procedure with a scan tool.
The scan tool instructs you to perform the following:
4.1. Accelerate to wide open throttle (WOT).
4.2. Release throttle when fuel cut-off occurs.
4.3. Observe fuel cut-off for applicable engine.
4.4. Engine should not accelerate beyond calibrated RPM value.
4.5. Release throttle immediately if value is exceeded.
4.6. Block drive wheels.
4.7. Set parking brake.
4.8. DO NOT apply brake pedal.
4.9. Cycle ignition from OFF to ON.
4.10. Apply and hold brake pedal.
4.11. Start and idle engine.
4.12. Turn A/C OFF.
4.13. Vehicle must remain in Park or Neutral.
4.14. The scan tool monitors certain component signals to determine if all the conditions are met to continue with the procedure.
The scan tool only displays the condition that inhibits the procedure.
The scan tool monitors the following components:
• CKP sensors activity--If there is a CKP sensor condition, refer to the applicable DTC that set.
• Camshaft position (CMP) sensor activity--If there is a CMP sensor condition, refer to the applicable DTC that set.
• Engine coolant temperature (ECT)--If the ECT is not warm enough, idle the engine until the engine coolant temperature reaches the correct temperature.
Enable the CKP system variation learn procedure with a scan tool.
Important:
While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate.
The engine control is returned to the operator and the engine responds to throttle position after the learn procedure is complete.
Another way to do CKS Relearn when parker, engine running :
Accelerate to WOT.
Release when the fuel cut-off occurs. (hit rev limiter)
Send CKP relearn command via scanner
Test in progress
The scan tool displays Learn Status:
Learned this ignition. If the scan tool indicates that DTC P0315 ran and passed, the CKP variation learns procedure is complete. If the scan tool indicates DTC P0315 failed or did not run, refer to DTC P0315 .
If any other DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for the applicable DTC that set.
Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.
The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether DTC P0315 is set:
• A CKP sensor replacement
• An engine replacement
• A ECM replacement
• A harmonic balancer replacement
• A crankshaft replacement
• Any engine repairs which disturb the CKP sensor relationship
You sure the new CKP is the right one for your engine ?
Is it from a quality vendor ?
Cannot do a CKS relearn if ANY DTCs have tripped, so clear them before starting the CKP relearn
Did you do as I mentioned, is ECT sensor reporting correct coolant temp, must be over 160F deg
With scanner do other sensors like MAF, MAP, O2s values look normal
Cannot do CKP relearn during OL
Possible the scanner you're using is sending the CKP relearn command ?
Here are a couple of GM ways do to CKP relearn process, not sure if these are correct for your year/engine
Crankshaft Position System Variation Learn
Install a scan tool.
Monitor the engine control module (ECM) for DTCs with a scan tool.
If other DTCs are set, except DTC P0315, refer to Diagnostic Trouble Code (DTC) List - Vehicle for the applicable DTC that set.
Select the crankshaft position (CKP) variation learn procedure with a scan tool.
The scan tool instructs you to perform the following:
4.1. Accelerate to wide open throttle (WOT).
4.2. Release throttle when fuel cut-off occurs.
4.3. Observe fuel cut-off for applicable engine.
4.4. Engine should not accelerate beyond calibrated RPM value.
4.5. Release throttle immediately if value is exceeded.
4.6. Block drive wheels.
4.7. Set parking brake.
4.8. DO NOT apply brake pedal.
4.9. Cycle ignition from OFF to ON.
4.10. Apply and hold brake pedal.
4.11. Start and idle engine.
4.12. Turn A/C OFF.
4.13. Vehicle must remain in Park or Neutral.
4.14. The scan tool monitors certain component signals to determine if all the conditions are met to continue with the procedure.
The scan tool only displays the condition that inhibits the procedure.
The scan tool monitors the following components:
• CKP sensors activity--If there is a CKP sensor condition, refer to the applicable DTC that set.
• Camshaft position (CMP) sensor activity--If there is a CMP sensor condition, refer to the applicable DTC that set.
• Engine coolant temperature (ECT)--If the ECT is not warm enough, idle the engine until the engine coolant temperature reaches the correct temperature.
Enable the CKP system variation learn procedure with a scan tool.
Important:
While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate.
The engine control is returned to the operator and the engine responds to throttle position after the learn procedure is complete.
Another way to do CKS Relearn when parker, engine running :
Accelerate to WOT.
Release when the fuel cut-off occurs. (hit rev limiter)
Send CKP relearn command via scanner
Test in progress
The scan tool displays Learn Status:
Learned this ignition. If the scan tool indicates that DTC P0315 ran and passed, the CKP variation learns procedure is complete. If the scan tool indicates DTC P0315 failed or did not run, refer to DTC P0315 .
If any other DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for the applicable DTC that set.
Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.
The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether DTC P0315 is set:
• A CKP sensor replacement
• An engine replacement
• A ECM replacement
• A harmonic balancer replacement
• A crankshaft replacement
• Any engine repairs which disturb the CKP sensor relationship
Ok fyi
I took the 2 cam sensors on the #1 bank drv side off
Left the plug connected. Turned ign on no start.
I back probed the 12v supply and signal wire. It showed 5.1vs
I then took my socket wrench and put it up to magnet on sensor it was showing 5.1v still.As I took wrench away 0.0Vs I tried it several times and every time is same.
According to a few videos I've watched on YouTube. It should be the opposite. As I put socket wrench to magnet it should read 0v.and go back to 5v after removing wrench.
This can't be right?
Both sensors int and ex do same thing.
Does this make sense?
I took the 2 cam sensors on the #1 bank drv side off
Left the plug connected. Turned ign on no start.
I back probed the 12v supply and signal wire. It showed 5.1vs
I then took my socket wrench and put it up to magnet on sensor it was showing 5.1v still.As I took wrench away 0.0Vs I tried it several times and every time is same.
According to a few videos I've watched on YouTube. It should be the opposite. As I put socket wrench to magnet it should read 0v.and go back to 5v after removing wrench.
This can't be right?
Both sensors int and ex do same thing.
Does this make sense?
Process told you system not satisfied.
As I have posted you need to find out if it is a coolant temp issue or another sensor a problem
If the scanner is worth a damn, engine loop PID has been around since the 1990s and should be supporting that PID
Maybe they called the PID something else, or contact that vendor and ask them if they support a generic SAE OBD PID ?
As I have posted you need to find out if it is a coolant temp issue or another sensor a problem
If the scanner is worth a damn, engine loop PID has been around since the 1990s and should be supporting that PID
Maybe they called the PID something else, or contact that vendor and ask them if they support a generic SAE OBD PID ?
Ok I'll find out about the PID.
I do know if I keep hood open the temp according to my scanner is around 142° if I close hood it rises to about 185 to 200
I noticed the monitoring the coolant sensor it's staying cool
I may have a stuck open therm.
I do know the crk is new and it needs a relearn if I can get the PCM to go CL ?
Tomorrow I'm going to replace the O2 sensor bank 1 sensor 2
Then I'll clear all codes and try again to do a relearn on crk to PCM.
I also have a TCM code just telling me I need a trans fluid change.
I don't think that has anything to do with engine running rough.
I'm not getting any cam sensor codes or injector codes just the P0300 which I'm sure is due to the P0017.
I'll update tomorrow after.
Thanks for the help!
I do know if I keep hood open the temp according to my scanner is around 142° if I close hood it rises to about 185 to 200
I noticed the monitoring the coolant sensor it's staying cool
I may have a stuck open therm.
I do know the crk is new and it needs a relearn if I can get the PCM to go CL ?
Tomorrow I'm going to replace the O2 sensor bank 1 sensor 2
Then I'll clear all codes and try again to do a relearn on crk to PCM.
I also have a TCM code just telling me I need a trans fluid change.
I don't think that has anything to do with engine running rough.
I'm not getting any cam sensor codes or injector codes just the P0300 which I'm sure is due to the P0017.
I'll update tomorrow after.
Thanks for the help!
If the coolant temp is reporting cold than reason PCM would not go into CL and PCM then is ignoring the feedback sensors
so fuel trims would be way off and also OL would prevent CKP relearn being completed so before doing anything else is look and see maybe wiring issue to the ECT sensor has a problem, its connector maybe came off or sensor is bad
Does the dash have a ECT gauge ?
Look at the ECT of scanner PID would be helpful as what it reports
Again, ECT has to report over150F deg to allow PCM to switch to CL
As their email stated, if needed select the I/M SMOG function would also show if engine is in OL or CL
Locate the engine loop PID as that will be very useful in debugging
TCM DTCs would not be the cause of how engine is running, stuck in OL would
so fuel trims would be way off and also OL would prevent CKP relearn being completed so before doing anything else is look and see maybe wiring issue to the ECT sensor has a problem, its connector maybe came off or sensor is bad
Does the dash have a ECT gauge ?
Look at the ECT of scanner PID would be helpful as what it reports
Again, ECT has to report over150F deg to allow PCM to switch to CL
As their email stated, if needed select the I/M SMOG function would also show if engine is in OL or CL
Locate the engine loop PID as that will be very useful in debugging
TCM DTCs would not be the cause of how engine is running, stuck in OL would
Yes I have checked ECT on scanner and when I was trying to do the relearn it was at 190° to 200° with hood closed. Still it states not satisfied at end of relearn.
I'm trying to isolate crk sensor on scanner to see if it's registering. Since it's a replacement.
I figure since car is starting it must be..
i really just need the PCM to go into CL then I can hopefully do relearn and check other sensors on a health report.
I'll try all that this morning. And report back
Thanks again!
I'm trying to isolate crk sensor on scanner to see if it's registering. Since it's a replacement.
I figure since car is starting it must be..
i really just need the PCM to go into CL then I can hopefully do relearn and check other sensors on a health report.
I'll try all that this morning. And report back
Thanks again!
Ok I just did a scan and same codes came up P0300 P0017
I cleared them and did a diagnostic
Same trans code came up and a P0128 ECT below normal range.
PCM went into CL.
I check temp and it was 187°
So that's confusing.
I tried to do a relearn on crk but when I click on special features it only shows a relearn for the trans.
Crk isn't there anymore.
Cat is still running rough
This is rattling my brain!
I cleared them and did a diagnostic
Same trans code came up and a P0128 ECT below normal range.
PCM went into CL.
I check temp and it was 187°
So that's confusing.
I tried to do a relearn on crk but when I click on special features it only shows a relearn for the trans.
Crk isn't there anymore.
Cat is still running rough
This is rattling my brain!
You need to focus your debugging to coolant temp reported to the PCM
Something is erratic
Print this out and following it closely to pinpoint if the issue is the Tstat, intake air temp sensor, ECT sensor or wiring
Monitor both ECT and IAT sensors with scanner, and se if the values change oddly
Best of scanner has a record mode to later replay to analyze
Other DTC is for CKP, and cannot do its relearn as long as a ECT issue
Just think of all the OBD2 you're learning with this
This generic trouble code can affect most makes and models of vehicles.
The code is signaled when your powertrain control module detects an unusual temperature reading while your engine is running. Typically, it’s signaled when your thermostat isn’t reading any temperature or is reading an incorrect temperature.
This conclusion is reached based on the intake air temperature sensor reading, the length of time your vehicle has been running and the engine coolant temperature sensor reading.
While there is a small chance that there is an issue with the running temperature of your engine, by far the most common issue with trouble code P0128 is a faulty thermostat.
The exact location of the thermostat and issues related to a damaged thermostat may vary depending on your vehicle.
For most vehicles, trouble code P0125 is related to this issue as well.
Common Symptoms
Your thermostat is an essential component for regulating coolant temperature and checking for more serious issues with your engine. However, a damaged thermostat won’t typically cause any performance issues.
So, what does the code P0128 mean? You’ll likely see your malfunction indicator lamp illuminate. You may also experience a longer amount of time for your engine to warm up, or the temperature dropping while you’re driving at high speeds.
The most important reason to replace your thermostat is to keep your coolant system working properly and to catch any early signs of engine damage.
Likely Causes
The most likely cause is a leaking or stuck open thermostat. Related issues would typically signal another error code, so this should be one of the first areas to inspect. Consult your service manual to find the exact location of your thermostat.
However, before you replace your entire thermostat, inspect these other areas as well.
Low engine coolant can alter the engine running temperature enough to signal trouble code P0128.
Your intake air temperature sensor, coolant temperature sensor and coolant fan could also signal this trouble code, so these should be inspected after you look over your thermostat and coolant level.
How to Fix P0128
Start with the easiest repair solution, which is low coolant levels.
Before you start, turn off your engine and wait until it’s sufficiently cool to open your coolant reservoir. Under normal operation, a coolant system is pressurized.
Opening a hot coolant system could cause burns and other injuries if you aren’t careful.
Once your engine and coolant system are cool enough to inspect safely, check the levels and strength of your coolant and compare it with the recommended levels in your service manual.
While the thermostat is one of the most likely issues with this trouble code, it can be difficult to inspect your thermostat.
A faulty thermostat may not have any visible signs of damage.
Before you replace your thermostat, it’s a good idea to inspect these other systems:
Something is erratic
Print this out and following it closely to pinpoint if the issue is the Tstat, intake air temp sensor, ECT sensor or wiring
Monitor both ECT and IAT sensors with scanner, and se if the values change oddly
Best of scanner has a record mode to later replay to analyze
Other DTC is for CKP, and cannot do its relearn as long as a ECT issue
Just think of all the OBD2 you're learning with this
This generic trouble code can affect most makes and models of vehicles.
The code is signaled when your powertrain control module detects an unusual temperature reading while your engine is running. Typically, it’s signaled when your thermostat isn’t reading any temperature or is reading an incorrect temperature.
This conclusion is reached based on the intake air temperature sensor reading, the length of time your vehicle has been running and the engine coolant temperature sensor reading.
While there is a small chance that there is an issue with the running temperature of your engine, by far the most common issue with trouble code P0128 is a faulty thermostat.
The exact location of the thermostat and issues related to a damaged thermostat may vary depending on your vehicle.
For most vehicles, trouble code P0125 is related to this issue as well.
Common Symptoms
Your thermostat is an essential component for regulating coolant temperature and checking for more serious issues with your engine. However, a damaged thermostat won’t typically cause any performance issues.
So, what does the code P0128 mean? You’ll likely see your malfunction indicator lamp illuminate. You may also experience a longer amount of time for your engine to warm up, or the temperature dropping while you’re driving at high speeds.
The most important reason to replace your thermostat is to keep your coolant system working properly and to catch any early signs of engine damage.
Likely Causes
The most likely cause is a leaking or stuck open thermostat. Related issues would typically signal another error code, so this should be one of the first areas to inspect. Consult your service manual to find the exact location of your thermostat.
However, before you replace your entire thermostat, inspect these other areas as well.
Low engine coolant can alter the engine running temperature enough to signal trouble code P0128.
Your intake air temperature sensor, coolant temperature sensor and coolant fan could also signal this trouble code, so these should be inspected after you look over your thermostat and coolant level.
How to Fix P0128
Start with the easiest repair solution, which is low coolant levels.
Before you start, turn off your engine and wait until it’s sufficiently cool to open your coolant reservoir. Under normal operation, a coolant system is pressurized.
Opening a hot coolant system could cause burns and other injuries if you aren’t careful.
Once your engine and coolant system are cool enough to inspect safely, check the levels and strength of your coolant and compare it with the recommended levels in your service manual.
While the thermostat is one of the most likely issues with this trouble code, it can be difficult to inspect your thermostat.
A faulty thermostat may not have any visible signs of damage.
Before you replace your thermostat, it’s a good idea to inspect these other systems:
- Intake air temperature sensor
- Engine coolant temperature sensor
- Cooling fan
- Faulty wiring to ECT or IAT
Ok I checked coolant level in recovery and it's just above the cool indicator. âś”
I need to find the IAT valve.
I know the cooling fan works.
I heard it come on while engine was running. Temp gauge was in the middle.
So I'll find the AIT and check it
What confuses me is even after I cleared the DTC's
I went to special functions and
The CRK sensor wasn't on the list anymore for relearn.
Like before. Could one of the times I tried relearn it worked?
If so why is car running rough?
I hope I'm not going to have to do timing chains.
I'm going to try pulling up live stream and graphs of injectors,O2's
And see what range they are in
And fuel trims.
I may change thermostat just because.
I need to find the IAT valve.
I know the cooling fan works.
I heard it come on while engine was running. Temp gauge was in the middle.
So I'll find the AIT and check it
What confuses me is even after I cleared the DTC's
I went to special functions and
The CRK sensor wasn't on the list anymore for relearn.
Like before. Could one of the times I tried relearn it worked?
If so why is car running rough?
I hope I'm not going to have to do timing chains.
I'm going to try pulling up live stream and graphs of injectors,O2's
And see what range they are in
And fuel trims.
I may change thermostat just because.
Not sure I would trust that scanner
Shows STFT B1 at -39% rich and B2 30% lean
That is nuts as that much of an imbalance from one head to the other would trip multi fuel trim DTCs
Also show MAF output at 45 lbs/hr, not a chance, esp if at idle would be more like 1 lb/hr
Maybe you need to connect again as to your car, as maybe the scanner somehow connecting as another car type ?
And why CKP test not showing up in the menu
As to I/M, it states that the main 4 SMOG functions all fail with non-completes
Scanner is called Launch ?
What model ?
Shows STFT B1 at -39% rich and B2 30% lean
That is nuts as that much of an imbalance from one head to the other would trip multi fuel trim DTCs
Also show MAF output at 45 lbs/hr, not a chance, esp if at idle would be more like 1 lb/hr
Maybe you need to connect again as to your car, as maybe the scanner somehow connecting as another car type ?
And why CKP test not showing up in the menu
As to I/M, it states that the main 4 SMOG functions all fail with non-completes
Scanner is called Launch ?
What model ?
Could be the scanner got things in a screwy mode
Might disconnect one side of car's battery for like 5 seconds to resync the PCM
and then see if scanner/PCM works correctly again
I saw reviews on Amazon for this model and 12 % reviews are only 1 star with problems
GM trips fuel trim DTCs about +13 lean and think about -12% rich so what scanner reported and no DTCs
feels like scanner is at fault as no way PCM would see about 80% different spread from B1 to B2
BTW
does that scanner support software updates and if so have you checked the scanner when connected to a P/C on internet for updates check and installs if there are new updates ?
Might disconnect one side of car's battery for like 5 seconds to resync the PCM
and then see if scanner/PCM works correctly again
I saw reviews on Amazon for this model and 12 % reviews are only 1 star with problems
GM trips fuel trim DTCs about +13 lean and think about -12% rich so what scanner reported and no DTCs
feels like scanner is at fault as no way PCM would see about 80% different spread from B1 to B2
BTW
does that scanner support software updates and if so have you checked the scanner when connected to a P/C on internet for updates check and installs if there are new updates ?
Yes it does do updates and I had a notify it needed up dates so I did them!
I have another scan tool.its more basic but does live data and IM
I plugged it in and same DTC's
I check live data and It says PCM is in CL
I'll send pics of data. Looks the same on fuel trims
I cleared DCT and they came right back. P0017 and P0300
I'll send pics.
![Image]()
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I have another scan tool.its more basic but does live data and IM
I plugged it in and same DTC's
I check live data and It says PCM is in CL
I'll send pics of data. Looks the same on fuel trims
I cleared DCT and they came right back. P0017 and P0300
I'll send pics.
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