: 05' STS. Little help with P0102 please



BJD210
08-07-09, 07:45 PM
I recently bought an out of state STS N* with 50Kmi. After a couple days of driving everything was checking out, that is, until the first time I revved the motor in neutral/park. The motor missed/backfired 3-4 times as it went up in rpm's. This has not changed in the 900mi I have driven since I first noticed the problem. I cannot hold the rpms at any level above 4k, it just starts to bog down. It is a VERY similar sound/fell of a rev limiter.

I was excited when the check engine light finally came on about 75mi ago. I figured that I could now diagnose and fix the problem. The only code that came up was P0102, Low input on MAF circuit. I removed and cleaned the MAF, cleaned the throttle body and put it back together. The issue seemed to improve but it was still not right and the SES was not going away. I then replaced the MAF with a new-used one but I still get the same code fired off immediately after clearing it.

I have not been able to isolate any vacuum leaks
The motor runs the exactly the same with or without the MAF plugged in
I cannot feel/hear this happening when the motor is under load
It has a very slight idle “miss” only when it’s a cold start.
When I took the MAF out the first time there was no gasket between the MAF and the air box and the screws holding the MAF to the airbox were about half thread in leaving a gap.

I would appreciate any insight. Thanks

Ranger
08-07-09, 08:52 PM
Do a search for plenum and check it.

BJD210
08-07-09, 10:38 PM
Do a search for plenum and check it.

Ive come across posts talking about plenum issues a few times while searching my problem. i will check into that

I havent found much of anything on the 05+ N*'s. I assume they are very close but is the pre 05' 4.6l close enough of a build for me to work off that info?

JimD
08-07-09, 11:08 PM
....that is, until the first time I revved the motor in neutral/park....I cannot hold the rpms at any level above 4k, it just starts to bog down. It is a VERY similar sound/fell of a rev limiter.That's because there is a rev limiter to protect the transmission from idiots that want to rev the engine in N and pull the shifter into D. But I question the 4,000 RPM figure; it's too high based on my experience.

...The only code that came up was P0102, Low input on MAF circuit. I removed and cleaned the MAF, cleaned the throttle body and put it back together. The issue seemed to improve but it was still not right and the SES was not going away. I then replaced the MAF with a new-used one but I still get the same code fired off immediately after clearing it.
P0102 - Mass Air Flow (MAF) Sensor Circuit Low Frequency
Since you have replaced the MAF to no avail, I suggest you very carefully inspect the associated wiring and connectors.

The motor runs the exactly the same with or without the MAF plugged inAnother wiring/connector issue clue.

JimD
08-07-09, 11:16 PM
....I havent found much of anything on the 05+ N*'s. I assume they are very close but is the pre 05' 4.6l close enough of a build for me to work off that info?
Can't offer anything here expect a reminder your car is rear wheel (or possibly all wheel) drive and my Northstar experience is limited to front wheel drive models.

There will be differences.

Helm publishes the Service Manuals for GM (and others). Certainly worth the money for a serious DIYer.

BJD210
08-07-09, 11:28 PM
That's because there is a rev limiter to protect the transmission from idiots that want to rev the engine in N and pull the shifter into D. But I question the 4,000 RPM figure; it's too high based on my experience.

P0102 - Mass Air Flow (MAF) Sensor Circuit Low Frequency
Since you have replaced the MAF to no avail, I suggest you very carefully inspect the associated wiring and connectors.
Another wiring/connector issue clue.

would this rev limiter also be the cause of my motor missing/rev limiting 3-4 times as it goes up the rpm range starting at about 2k? it is a very unsettling sound and i would figure there would be posts all over the board about it if it were a common occurrence

I was planning on peeling back the looms tomorrow to check the wiring. Is there any way I can test resistance or voltage at the MAF connector. That would be a lot easier

Ranger
08-08-09, 10:40 AM
I forgot all about the rev limiter. The rev limiter should not cause any misfires. It simply shuts off the fuel injectors at 4K in neutral.

AJxtcman
08-08-09, 05:49 PM
I see this all the time.

First check to see it the intake bolts are loose. This is the most common issue

Next check to make sure the dip stick is in all the way :suspense: Yes if the o-ring is not sealing the dip stick in the tube it sets this code also. :want: Lube techs. Grrrrrr

Next check the air intake system for a loose connection. This is a cold out side temp issue. Mid winter up north

Check the air filter box to make sure it is correctly attached at the bottom

BJD210
08-08-09, 11:23 PM
so I didn't have a chance to dig into it today but I did have to pull over twice on the freeway. first time it happened I was accelerating pretty hard on an on ramp. all of a sudden it just stopped accelerating and displayd "engine power reduced" on the DIC. i pulled over and it died once I stopped. I pressed the start button and it fired up as normal. 10 minutes later I was cruising at 55mph and with no warning the motor died. I was able to put it in neutral and start while rolling and again it fired back up like it hadn't missed a beat.

AJxtcman
08-09-09, 01:18 PM
so I didn't have a chance to dig into it today but I did have to pull over twice on the freeway. first time it happened I was accelerating pretty hard on an on ramp. all of a sudden it just stopped accelerating and displayd "engine power reduced" on the DIC. i pulled over and it died once I stopped. I pressed the start button and it fired up as normal. 10 minutes later I was cruising at 55mph and with no warning the motor died. I was able to put it in neutral and start while rolling and again it fired back up like it hadn't missed a beat.

Is the RPM going to 0 or just down to idle RPM?

BJD210
08-10-09, 10:15 AM
Is the RPM going to 0 or just down to idle RPM?

Kind of... I have seen the "engine power reduced" message before when I started the car without a vacuum line or the MAF sensor hooked up. It immediately displayed the warning and if I didn't keep my foot on the gas it would die. That is what happened the first time. The second time it just straight shut down. I didn't even feel it, all of a sudden I went to press on the gas and nothing happened. I looked down and the RPM's were at 0.

For now I am going to attribute these two incidents to the fact I have been messing around with the vacuum lines and sensors and so on. First I am going to run through everyone’s suggestions tonight and see if I can’t get that code to clear. Hopefully that will solve my issues.

cobra671
08-13-09, 01:35 PM
so I didn't have a chance to dig into it today but I did have to pull over twice on the freeway. first time it happened I was accelerating pretty hard on an on ramp. all of a sudden it just stopped accelerating and displayd "engine power reduced" on the DIC. i pulled over and it died once I stopped. I pressed the start button and it fired up as normal. 10 minutes later I was cruising at 55mph and with no warning the motor died. I was able to put it in neutral and start while rolling and again it fired back up like it hadn't missed a beat.

You know, I've had these same issues shortly after I puchased my 05 with N*. But the difference was that my car would just shut off at any point when I came to a stop and it dropped to idle rpm. I sort of got used to it, when it it did it, I would just turn it off completely (ACC switch) and start her right back up.

I eventually took it to the dealer where they replaced the wire harness that went to the throttlebody. It hasn't happened since. It may be a cadillac thing, idk. Good luck with yours.

I would freak if my car shut down while on the freeway, I'm glad nothing bad happened to you.

BJD210
08-13-09, 02:30 PM
I am not excited to trace the harnesses so I am saving that for last. I cannot get the car into my warehouse/shop right this second so I have been putting it off all together.

And yes I freaked, it wasn't because I couldn't acclereate to get away from the merging idioit that almost hit me. I was more freaked about the State Trooper that was posted up down the road. Lets just say my temporory registration was past its expiration and Troopers around here don't give warnings. I would be walking home in the rain if I had to bring the car to a stop near him. I don't know if he saw everything but I basically flashed him with my HID's from 20' away when I went to restart the car. He didn't follow but I put the car away until my Title showed up and I could pay my registration. Not a fun day.

BJD210
10-08-09, 10:47 PM
Update.

Gotta Love Cadillac, They fix themselves:)

Anyways, I checked, cleaned or replaced anything I could think of except for the harnesses with no luck. Every time I attempted something new I would reset codes or leave power disconnected for 24hrs. No matter what I did it would throw the code immediately. The computer was consistently putting the motor into "reduced power" when I gave it heavy acceleration. I gave in and just drove it for a couple weeks without messing with it. Just before I was going to make an expensive date with a Tech2 I disconnected the battery to hook up a couple amps and when I restarted the car the light was gone. I have not seen the light in the 900mi since and I cannot reproduce any issues I had before.

Whatever, I completely expect to see the code again but for now I will keep my fingers crossed

tateos
10-09-09, 01:51 PM
Thanks for the update.

BJD210
10-30-09, 05:12 PM
Update II

I replaced some bulbs the other day. When I was done the light was back on. The only thing I touched other than the bulb harnesses was the air box. I had to unbolt it but I didn't take it apart or detacht it from the rest of the intake system. I have completely dissasmbled the box and checked over every inch. no defects.

The spectacular news is... I just found out that my car is a prior CPO and its under warrenty for another 3 years or 47kmi. All I have to do is drop it off at the dealer and tell them to figure it out. I feel like I just won the lottery!

I will post the dealers findings after I take it in.

Thanks to GMCentral.com for the VIN check that showed the warrenty history.