Need help with 'Reduced Power' msg when I give throttle a bit too quickly

[h3lover]

As soon as I press the gas pedal (accelerator) a bit too quickly, check engine light comes on and I see 'Reduced Power' and 'Service Stab System' messages and driving becomes sluggish. On scanning, it shows P0300 (Random misfire) and P0606 (ECM/PCM processor) codes. Surprising thing is, if I use cruise control (before these messages pop up), these messages never pop up even if I drive 300 miles on the highway (tried multiple times).

So far I have changed battery and terminals on my 08 hummer h3 3.7L. Spark plugs were changed 2yr/10,000 miles back. How should I troubleshoot/fix this issue?

 

[Happy Hummer]

Verify your live date on ecm and etc. Something isn't correlating between em or your ecm is spanked internally.
Did you recently mess with intake related items? Such as MAF? Air intake? Electronic throttle control? Coolant temp sensor?

 

[Happy Hummer]

Added aftermarket cr@p (jmho)?

 

[h3lover]

Verify your live date on ecm and etc. Something isn't correlating between em or your ecm is spanked internally.
Did you recently mess with intake related items? Such as MAF? Air intake? Electronic throttle control? Coolant temp sensor?

Thanks for replying. I am going to check live date on ecm. This has been happening for than 4 months but I was away during summers to look at it. My battery was draining fast so I replaced battery and terminals and drain seem to have gone now. Bit reduced power comes always if I hit throttle a but quickly. Same thing does not happen when I am in cruise control.
What else should I look at besides live date on ecm?

 

[h3lover]

Added aftermarket cr@p (jmho)?

no aftermkt stuff except auto-start but that I have for over 5 years

 

[Happy Hummer]

Your ecm to ETC as a correlation issue. Or ecm has internal errors. Verify wiring with DVM and test light.

 

[h3lover]

Your ecm to ETC as a correlation issue. Or ecm has internal errors. Verify wiring with DVM and test light.

will give that a shot!

 

[Jeepwalker]

You might do a compression test too. It's somewhat common on these engines the center cylinders burn valves. Esp #3. Mine's had low compression on #3 for a few tens of thousands of miles. The ECM keeps track of misfires and when they get high enough over a given period of time (3 seconds? 4 seconds? Something like that), once the misfires cross a threshold, a mis-fire count trouble code is generated. It could also be related to a flaky coil, a hairline crack in a coil, cracked plug... or burnt wire.

 

[Jeepwalker]

As far as the other errors go, has your tk ever been in an accident? There's a sensor that monitors intertia and stability under the driver's seat. Those have been known to go flaky for some forum members in the past. You might do a general google search on those errors and see what comes up. Check real-time data if your scanner lets you. You can remove the driver's seat (easy) and get to the sensor I 'think'.

There's a ground wire next to that sensor on the beam where the front 'outside' bolt holds the driver's seat. So it's right behind that bolt on top. You might have to pull off the sill plastic plate to lift the carpet enough to get to it (with the Dr seat out). I would ensure that ground wire is 'good' and the connector pins aren't corroded .....esp before replacing that module. I had all kinds of flaky stuff going on, and the window switch 'issue' plaguing my H3 ...all of which went away years ago (and never returned) after I fixed that ground (the wire itself was corroded behind the connector). And your H3's sensor could have a corroded wire/pin too. You see, if the sunroofs leaked a bunch of times, it can corrode connectors over time. Also, make sure your truck's battery->body grounds are very good, or add another ground strap. There are ground all over on the inside..that's how important grounds are to these vehicles...and any vehicle with modern electronics. At least look at those things. Good luck

 

[h3lover]

compression test

Thanks, I intend to do a compression test and inspect coils and plugs...not sure how to track down a burnt wire though

 

[h3lover]

As far as the other errors go, has your tk ever been in an accident? There's a sensor that monitors intertia and stability under the driver's seat. Those have been known to go flaky for some forum members in the past. You might do a general google search on those errors and see what comes up. Check real-time data if your scanner lets you. You can remove the driver's seat (easy) and get to the sensor I 'think'.

There's a ground wire next to that sensor on the beam where the front 'outside' bolt holds the driver's seat. So it's right behind that bolt on top. You might have to pull off the sill plastic plate to lift the carpet enough to get to it (with the Dr seat out). I would ensure that ground wire is 'good' and the connector pins aren't corroded .....esp before replacing that module. I had all kinds of flaky stuff going on, and the window switch 'issue' plaguing my H3 ...all of which went away years ago (and never returned) after I fixed that ground (the wire itself was corroded behind the connector). And your H3's sensor could have a corroded wire/pin too. You see, if the sunroofs leaked a bunch of times, it can corrode connectors over time. Also, make sure your truck's battery->body grounds are very good, or add another ground strap. There are ground all over on the inside..that's how important grounds are to these vehicles...and any vehicle with modern electronics. At least look at those things. Good luck Once

 

[h3lover]

Thanks for the detailed reply. I will check all of these esp.ly the ground under drivers seat. Intend to start with adding another ground to the battery

 

[Vaderdad]

Well what were your results? Did you check grounding wire on the Yaw sensor ?

 

[4speedfunk]

Years ago CaseyS let me drive his Cummins swapped diesel H3., and it did the same thing. He was using the stock TPS connected to the throttle plate on the Cummins injector pump. He did this so he could retain the stock drive by wire pedal, and cruise control. The throttle body was still on the truck, but all it did was provide a TPS signal to the computer.

The issue was that the throttle return spring on the Cummins was too strong. The computer somehow sensed this spring pressure (via the TPS), and if the pedal resistance was too much…immediate limp mode. His only solution at that time, was to take off slower.

In summation: Limp mode can be initiated by too much physical resistance at the butterfly of the throttle body. Check the throttle body for any gunk build-up or sticking return spring. Also check the accelerator pedal. Start by testing the signals with a volt meter. Both of these devices should provide a smooth, linear voltage sweep throughout the movement range. The pedal signal AND the TPS signal must smoothly track each other. If either has a dead spot or sticking, the computer will sense the difference in voltages between the two, and initiate limp mode.