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1968 Deville convertible
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66 Posts
Discussion Starter #1
2007 DTS base with 93k on it.

Well my car originally had a p0171 and a p0174 code and I seen heard a leak coming from the intake area and ordered some gaskets. Figured for 13 bucks shipped I might as well change them out. I am mechanically inclined I have a 01 Vette that puts down a little over 800 hp stock block at that, a 1968 Deville(she a big girl) a 2004 Jeep Wrangler that's modded like crazy and a 03 Deville . All built by me. I figured this would be a walk in the park but nope not today.

I had the intake off in about 10 minutes if that, While I had it out I decided to clean all the grease and grime in that area. I scrubbed the throttle body, intake manifold and also decided to re wrap all the wiring with electrical tape and new wire loom since it literally broke into pieces once I touched it. I vacuumed everything up and made sure the surface area was prepped for the intake install. I got everything back in and primed the fuel pump to get pressure to the injectors and then I went to start the car and I could hear the throttle body blade actuating and the car stumbled. Ok no biggie tried it again and got it to run but had reduced engine power and I had codes p0452,p0641.p0641(not sure why I had it p0641 twice) I figured I didn't plug something back in but everything was good. I did break the hard plastic line from the intake manifold to the valve cover you know the one that's on the passenger side but I did fix it with some rubber hose and reused the connectors. Still car ran but reduced power and those same codes. I called it a day I had stuff to do

SO this am I I came back out and got codes P0452,P0641,P0340,P0452,P0641 now the car wont start but just cranks. Now P0340 was new BUT I noticed it only comes on when the car tries to start but will continue to crank even after they key is done turning. You know when you turn the key and let go well when I let go the car will try to continue to turn another few seconds so I figured that's what's causing that but I could be wrong. I did go back and take the manifold off again and to make sure I didn't mess up the crankshaft position sensor you figured if anything I would of gotten that code but I checked and it was fine and I took it out and cleaned it. I checked my previous work all no issues and went to try to start it and same thing with the same codes it wont even run just cranks. I did pull the camshaft sensor and cleaned it out it out and no changes to the starting. I said its a simple job but I managed to mess it up. I am using a generic ebay code reader BUT I do have a Tech 2 so maybe I need to relearn the cam shaft position? Help appreciated thanks

Shant

P0452 =Why all of a sudden would I get this everything was fine before and did not have this code before the intake manifold swap?

P0452
Fuel Tank Pressure Sensor Circuit Low Voltage

CADILLAC Possible Causes
  • Faulty Fuel Tank Pressure Sensor
  • Fuel Tank Pressure Sensor harness is open or shorted
  • Fuel Tank Pressure Sensor circuit poor electrical connection
-----------------------------------------------------------------------------------------------

I think if I fix this the rest will go away but not sure this I am unsure where to start with this or how to fix it
P0641 CADILLAC - 5 Volt Reference Voltage Incorrect
CADILLAC Possible Causes
  • Faulty Engine Control Module (ECM)
  • ECM harness is open or shorted
  • ECM circuit poor electrical connection
  • Shorted sensor on 5 volt circuit

P0340 CADILLAC Possible Causes
Camshaft Position Sensor Circuit Malfunction

I can test this via this vid. I have a tech 2 maybe I need to relearn it


hmmm no 12v coming out of the camshaft sensor harness,, That's the one on the side of the motor passenger side is this correct?

hmmmm not sure how to edit but never mind I have 5volts coming out of the harness on 2 spots. I guess it's not supposed to be 12?

Update. The battery was low on juice from cranking and having the lights on. I jumped it via the battery in the back. Went to crank the car and fired right up. Wtf? Battery had no issues before and not sure why jump would make it all better. I did disconnect the battery for 15 mins then reconnected just to see if that would help during all this which did nothing earlier into the trouble shooting. No check engine but my tech 2 and ebay scanner still show the p0340 as pending but no check engine light and runs great. I am getting the sevice traction control service brake assist and service stabilitrak. Again no codes to tell me which wheelbering that may be if that is the case I haven't dug to deep. So car is running normal now. No check engine light but I do have a pending p0340 camshaft position sensor error in both my readers. Just the sevice traction control service brake assist and service stabilitrak is flashing with the abs and traction control lights on. All comments welcome

Where the F is the edit button? Also I undid my gas cap and reinstalled while I had the car charging through another car I dont remember if it was loose but I think that was the p0452 but again that was sying 5v sort. Ok enough I'm done for the night.

sevice traction control service brake assist and service stabilitrak is now gone. Basically the car fixed itself. awesome
 

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2006 DTS perf
2006 DTS Performance Lux III
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1,014 Posts
In the future when disconnecting sensors to do engine repairs disconnect the battery. Even though the ignition is off the ecm is still active. Also a weak battery causes all kinds of problems with the modules. Whenever a code is active the traction control shuts down. Glad everything worked out. Use the tech 2 and clear all the codes that are stored or pending. Many stored faults won't cause the check engine light to come on.
 

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Registered
1968 Deville convertible
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66 Posts
Discussion Starter #3
Thanks Omac I should of known better the Corvette is finicky with it's electrical too but I figured I was only disconnecting the mas,map,throttle body I would of been fine. Yes I cleared them with the Tech 2. The only thing I have is the camshaft code and she takes a few more turns to start but I have one on order.
 

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2008 DTS
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108 Posts
I had a new valve cover gasket put on this week.New inner/outer tie rods front left. Drove it today a mile up the road and bingo,service traction low engine power came on.p0340-p0641. 5v referance 1 circuit my reader says, on the P0641,P0340 says intake camshaft position sensor circuit. Cleared the codes but the traction and cel still on. Battery was new this past summer i think,or certainly last spring anyway.
 

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2006 DTS perf
2006 DTS Performance Lux III
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1,014 Posts
I had a new valve cover gasket put on this week.New inner/outer tie rods front left. Drove it today a mile up the road and bingo,service traction low engine power came on.p0340-p0641. 5v referance 1 circuit my reader says, on the P0641,P0340 says intake camshaft position sensor circuit. Cleared the codes but the traction and cel still on. Battery was new this past summer i think,or certainly last spring anyway.
Check all the connections on the engine for any that are either not connected or partially connected.
 

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2008 DTS
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108 Posts
Check all the connections on the engine for any that are either not connected or partially connected.
I brought the car back to the place that did the work after looking at this thread and then youtube for videos.Although YOUTUBE didn't have an exact vid for an 08,i did at least see where the parts are located on the engine which in turn led me to believe they hit something unintentionally and may have knocked it out.Sure enough,it seems they clipped a wire back by the rear valve cover gasket which caused the issue.Took the car on a 30+mile round trip last night and so far,so good.
 

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2006 DTS perf
2006 DTS Performance Lux III
Joined
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1,014 Posts
I brought the car back to the place that did the work after looking at this thread and then youtube for videos.Although YOUTUBE didn't have an exact vid for an 08,i did at least see where the parts are located on the engine which in turn led me to believe they hit something unintentionally and may have knocked it out.Sure enough,it seems they clipped a wire back by the rear valve cover gasket which caused the issue.Took the car on a 30+mile round trip last night and so far,so good.
Awesome Glad it worked out for you.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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67,636 Posts
If you use the special Cadillac engine suspension jig the oil pan can be removed by hanging the engine and removing everything - cradle and suspension - under the engine. The tool is probably different from that used on my 2002 Seville -

There is a new, dedicated oil pan rail seal technique used. Find The TSB (Technical Service Bulletin) on the use of GM RTV Gray instead of the discontinued formed seal (it's not a gasket).
oil pan 7 quarts.jpg


engine support tool.gif
Engine suspension jig.gif
 

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2008 DTS
Joined
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108 Posts
If you use the special Cadillac engine suspension jig the oil pan can be removed by hanging the engine and removing everything - cradle and suspension - under the engine. The tool is probably different from that used on my 2002 Seville -

There is a new, dedicated oil pan rail seal technique used. Find The TSB (Technical Service Bulletin) on the use of GM RTV Gray instead of the discontinued formed seal (it's not a gasket). View attachment 575619

View attachment 575617 View attachment 575618
Geez.Who at GM ever thought this was a good idea for an oil pan gasket swap hopefully is now working in SIBERIA somewhere.Thanks for the info and diagrams.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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67,636 Posts
The Northstar engine is a modular assembly - the oil pan, halfcase, and upper cylinder block flanges are all machined as one strong, rigid assembly. Traditional gaskets do not allow that precision in machining, thus the flat seal surfaces and silicone seal grooves. The halfcase is a 20-bolt main bearing girdle and lower crank bearing carrier, plus some oil passages and structural parts.

If you ever disassemble the halfcase (thankfully, the lower end in a Northstar is bulletproof) there are special, dedicated procedures to get it all back together correctly. You're working on a setup comparable to the tweakiest Ferrari or Lamborghini ever built. It's NOT Grandma's Chevy 327. By a long shot.

The new seal process, using GM RTV Gray, was introduced to prevent the occasional original formed silicone seal leaks.

See Post #9.

Oil pan gasket.jpg
Lower crankcase (halfcase) lifted.gif
 

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2008 DTS
Joined
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108 Posts
The Northstar engine is a modular assembly - the oil pan, halfcase, and upper cylinder block flanges are all machined as one strong, rigid assembly. Traditional gaskets do not allow that precision in machining, thus the flat seal surfaces and silicone seal grooves. The halfcase is a 20-bolt main bearing girdle and lower crank bearing carrier, plus some oil passages and structural parts.

If you ever disassemble the halfcase (thankfully, the lower end in a Northstar is bulletproof) there are special, dedicated procedures to get it all back together correctly. You're working on a setup comparable to the tweakiest Ferrari or Lamborghini ever built. It's NOT Grandma's Chevy 327. By a long shot.

The new seal process, using GM RTV Gray, was introduced to prevent the occasional original formed silicone seal leaks.

See Post #9.

View attachment 575631 View attachment 575633
"GM RTV GRAY" Is that a new gasket or a different seal altogether?? Where do I BUY ONE?
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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67,636 Posts

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2008 DTS
Joined
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108 Posts
It's RTV - Room Temperature Vulcanizing - silicone rubber sealant. Any parts store.

As advised, read Post #9 again..............

!

Thanks fellas. Local caddy dealer has i for 15 bucks. Online with shipping 11 bucks. Autoparts store has a silicone sealant just not GM specific. Don't know how much.
 

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Registered
2006 Cadillac CTS [] 2008 Cadillac DTS
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26 Posts
I had the same two lean codes, I've done downstream O2, and after the intake gasket the car was driving good... Then the codes came back with a rough idle. They come and go now. The fuel injectors were pretty gunked up the first time around and pressure clean them. I ordered new ones, and sparkplugs, and doing a valve cover job too since I already have the intake off again. Also having my mechanic check fuel pressure levels and the fuel filter. At 129,XXX miles I not surprised this happened. Previous owners when 8800 miles between oil changes which I'm sure didn't help the situation either. Think about installing a catch can to see if that helps it out any for the future.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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The FWD Northstar has no need for a cutesy catch can. The PCV orifice (late 2001 and later engines) in the right (rear) cam cover is well baffled. My 2002 gets over 6,500 miles to a quart of 5W-30 synthetic and I change it once a year because the car is now a garage queen. When I was logging 7,000 - 8,500 miles a year it still got the annual change because the OLM was at or above 40% at the oil year's end.

With favorable driving conditions it's entirely possible to safely run the oil to over 10,000 miles.

Here's the article with the early (pre-2000) OLM info, written by one of our members who was a GM Northstar Systems powertrain engineer.


Run a TopTier gasoline (Google it) and use a 20 oz. bottle of Chevron TECHRON at about 5,000 mile intervals.
 

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Registered
2006 Cadillac CTS [] 2008 Cadillac DTS
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26 Posts
The FWD Northstar has no need for a cutesy catch can. The PCV orifice (late 2001 and later engines) in the right (rear) cam cover is well baffled. My 2002 gets over 6,500 miles to a quart of 5W-30 synthetic and I change it once a year because the car is now a garage queen. When I was logging 7,000 - 8,500 miles a year it still got the annual change because the OLM was at or above 40% at the oil year's end.

With favorable driving conditions it's entirely possible to safely run the oil to over 10,000 miles.

Here's the article with the early (pre-2000) OLM info, written by one of our members who was a GM Northstar Systems powertrain engineer.


Run a TopTier gasoline (Google it) and use a 20 oz. bottle of Chevron TECHRON at about 5,000 mile intervals.
Ended up running the Chevron techron (black bottle) and a full tank of bp premium, which actually made the idle shake worse.
 
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