My service traction control and RPMs being.

ANONYMOUS

MEMBER
2008 CHEVROLET IMPALA
100,000 MILES

My service traction control and RPMs being reduced message has been coming on for over a week. I replaced the right front box hub because of a broken wire and it started in again

I found this post but what could it be?

The first thing a mechanic should look for is any damage to any wiring harnesses (there is a Technical Service Bulletin out about this).

If it isn't a voltage issue or the wire harnesses, then the next two things to look at would be your Throttle Position Sensor (requires replacing the throttle body) and the Accelerator Position Sensor (requires replacing your gas pedal).

The system in the Impalas is called a "Drive-by-wire" system. This means the accelerator position sensor and throttle position sensor work together. If either one of them act up, you get the warning messages you are seeing.

After changing any of these parts a relearn procedure must also be done so that the computer can relearn (or adjust) to the newer parts.

I opted to change my throttle body first, ooops. It turned out to be the accelerator (which is the cheaper part to replace by the way). Now it's running normally.

3 Replies

HMAC300

MECHANIC
48,601 POSTS

Scan for codes first

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Thursday, December 27th, 2012 AT 6:40 PM

THIS IS MIKE

MECHANIC
686 POSTS

Code 2127

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Sunday, December 30th, 2012 AT 12:11 AM

HMAC300

MECHANIC
48,601 POSTS

This can be a bad ecm but you need a protype tester to really see what is going on, it may be a bad wire that is shorted to ground or a bad connection. It needs the pro tpe so it can test one side the app 2 side of the throttle pedal assy. This is what the tsb says as well.
CAUSE

This� condition� may� be� caused� by� water� intrusion� into� the� instrument� panel� (IP)� to� body� harness� connector, � which� carries� the� APP� sensor� signals� to� the� ECM/PCM.� This� water� intrusion� results� in� a� voltage� difference� between
APP� Sensor� 1� and� APP� Sensor� 2� that� exceeds� a� predetermined� value� for� more� than� a� calibrated� period� of� time, � setting� P2138.

CORRECTION

NOTE: Aftermarket� equipment� can� generate� DTC� P2138� and/or� other� DTCs.

1. Verify� that� aftermarket� equipment� is� not� electrically� connected� to� any� of� the� APP� sensor� signal� or� low� reference� circuits� or� to� any� other� ECM/PCM� 5V� reference� or� low� reference� circuits.� Refer� to� Checking� Aftermarket
Accessories� in� SI.
2. Perform� the� Diagnostic� System� Check � Vehicle.
3. If� any� 5V� reference� DTCs are� set, � refer� to� Diagnostic� Trouble� Code� (DTC)� List � Vehicle.
4. If� any� 5V� reference� DTCs are� not� set, � proceed� to� Step� 3.
5. Locate� the� IP� to� body� harness� connector, � which� may� be� located� in� and� around� the� left� hand� kick� panel� area� or� inside� the� IP.� Depending� on� the� vehicle� and� model� year, � refer� to� Wiring� Systems� or� Power� and� Signal
Distribution� in� SI.

NOTE: Some� examples� of� potential� water� leaks� are:� A pillar� seals, � sunroof� drain� lines� (if� equipped)� and� windshield/cowl� sealing.

6. Inspect� for� a� water� leak� in� the� area.� If� necessary� use� a� water� hose� to� determine� the� source� of� the� leak.� Refer� to� General� Information� >� Water� Leaks� in� SI.
7. If� a� water� leak� is� observed, � repair� as� necessary.� Verify� the� effectiveness� of� the� repair.
8. Inspect� the� IP� to� body� harness� connector� terminals� for� corrosion� and� debris.� Refer� to� Testing� for� Intermittent� Conditions� and� Poor� Connections� in� SI.
9. If� any� corrosion� and/or� debris� is� observed, � repair� as� necessary.
10. After� completing� the� repair, � verify� the� proper� operation� of� the� system.� Depending� on� the� vehicle� and� model� year, � perform� the� Diagnostic� Repair� Verification� procedure� or� refer� to� Diagnostic� Trouble� Code� (DTC)� List
Vehicle� in� SI.
This can also be caused by aftermarket stuff being put on car.

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Sunday, December 30th, 2012 AT 1:25 AM