A Chevy Impala reduced engine power warning means the engine computer has cut back engine output. On 2006-2011 Impalas, a GM service bulletin ties this message to a throttle position sensor fault.
The warning can come from more than one fault, so start with your model year, engine code and stored trouble codes. Some owner reports also point to the accelerator pedal area, which is worth checking when the bulletin does not match your car.
Chevy Impala Reduced Engine Power: What the Message Means
The reduced engine power message tells you the engine computer is limiting output, usually with the check engine light (MIL) on. Owner reports often describe a traction control or StabiliTrak warning just before it appears.
When a Chevy Impala reduced engine power warning appears, GM’s bulletin describes it with the MIL lit and a stored trouble code. Owner reports describe the same pattern, though those are user reports, not manufacturer findings.
- The check engine light stays on alongside the Reduced Engine Power message.
- A traction control or StabiliTrak warning appears first or at the same time.
- Some owners say the car slowed on the highway, with speed falling to about 40 mph.
- A few reports describe the car losing power and coming to a stop, while others say the engine kept running with limited power.
The lights sometimes clear after the car sits, then return later. That pattern fits an intermittent fault, which is why the stored code matters more than the dashboard message alone. For the general picture, see the reduced engine power warning guide.
The Documented Cause: GM Bulletin 12-06-04-003
GM bulletin 12-06-04-003, dated December 2012, names DTC P2135 as the code behind the reduced power message. The code sets when the readings from the two throttle position sensors differ by more than a calibrated amount for over 2 seconds.
The NHTSA copy of GM bulletin 12-06-04-003 says the cause is TP Sensor 1 and TP Sensor 2 disagreeing beyond a calibrated value for more than 2 seconds. The bulletin is written for professional technicians, so treat it as a guide to what a shop should check for Chevy Impala reduced engine power, not a do-it-yourself manual. The P2135 code guide explains the code in general terms.
Check Whether Your Impala Matches the Bulletin
The bulletin covers 2006-2011 Chevrolet Impalas with engine codes LGD, LZ4, LZ8 or LZE. Check those points before you plan any repair, because a match narrows the search.
| Check | What the bulletin says | What to do |
|---|---|---|
| Model year | 2006-2011 Chevrolet Impala | Confirm the year from the registration or VIN |
| Engine code | LGD, LZ4, LZ8 or LZE | Compare with your engine code from build records or a dealer lookup |
| Trouble code | DTC P2135 set as current or in history | Read the codes with an OBD2 scanner |
| Warning | MIL on with the Reduced Engine Power message | Note whether the message appears with the light |
The same bulletin also lists 2006-2008 Chevrolet Malibu models, covered in the Chevy Malibu reduced engine power guide. A match does not prove the bulletin caused your Chevy Impala reduced engine power message. Other faults can set the same warning, so the code reading and the sensor check matter more than any single symptom.
Reading the Codes and the TP Sensor Agreement Check
Before any part is replaced, a scan tool should confirm that DTC P2135 is current or in history, and after the repair the TP Sensor 1 and 2 parameter should read Agree during a pedal test. A shop follows a fixed order for Chevy Impala reduced engine power diagnosis, and an owner can use the same checks to brief a technician.
- Confirm whether P2135 is set as current or in history.
- After the repair, clear the code with the scan tool, then watch the TP Sensor 1 and 2 Agree/Disagree parameter while you press the accelerator slowly to wide open throttle and back, several times.
- Then press the accelerator quickly from rest to wide open throttle and release, several times. The parameter should read Agree.
- If it still reads Disagree after the repair, the bulletin calls for replacing the throttle body assembly.
Clearing the code alone shows nothing about whether the sensors agree, so run the pedal test every time you clear a code.
What the Bulletin Repair Involves and What It Costs
The bulletin’s repair for Chevy Impala reduced engine power replaces the throttle position sensor cover, part number 19300180, and lists 1.2 labor hours. It does not start with a new throttle body (for what a full replacement costs, see throttle body replacement cost).
The procedure is not a simple swap. The technician removes the throttle body, cleans the bore and throttle plate with an approved engine cleaner, fits the new cover with its gasket, and reinstalls the body. The job ends with a throttle learn reset.
The bulletin also includes handling warnings. Technicians should not drop the throttle body or let the intermediate gear fall out, and they should not soak electronic throttle parts in cleaning solvents. If the gear falls out or the throttle body is dropped, the bulletin says to abort and install a new throttle body assembly.
- Labor time: 1.2 hours, including diagnosis, throttle body removal, cover replacement and the throttle learn reset.
- Warranty for 2007-2009 vehicles: the bulletin lists 5-year/100,000-mile Powertrain coverage.
- Warranty for 2010-2011 vehicles: the bulletin lists 3-year/36,000-mile Bumper-to-Bumper coverage.
- Warranty for 2006 vehicles: the bulletin lists separate emissions periods, such as 2-year/24,000-mile in the US.
The warranty periods come from a bulletin dated December 2012, so confirm current coverage with a dealer as of 2026-11-06. The bulletin lists no parts price, so no part cost is quoted here.
What Owners Report About Chevy Impala Reduced Engine Power
Owner reports on one complaint database list 13 cases of Chevy Impala reduced engine power for a 2009 Impala, a typical repair cost of $80, and mostly owners who were not sure of the fix. These are user reports, not verified repair records, and the database lists no diagnostic codes or recall numbers for them.
- One shop found a bad sensor near the top of the accelerator pedal assembly, replaced it, and the problem stopped.
- Another owner’s Chevy Impala reduced engine power scan pointed to the gas pedal sensor, but the dealer declined the repair because it could not reproduce the fault.
- Some owners report the warning appearing at highway speed, with the car slowing sharply.
The pedal location is worth checking. Ask the shop to read the pedal sensor values as well as the throttle sensor values, because owner reports point to both areas.
What to Do Next and When to Get the Car Checked
Read the codes first, check your VIN for open recalls, and get the car to a shop soon if Chevy Impala reduced engine power returns or power drops at speed. Those three steps separate a known bulletin fault from something else.
- Note the model year, engine code and whether the check engine light is on.
- Read the stored codes with an OBD2 scanner, or ask a shop to read them.
- Enter your VIN in the NHTSA recall lookup to check for open recalls.
- Ask the shop to confirm P2135 with a scan tool and to run the TP Sensor 1 and 2 Agree/Disagree check after any repair.
If the power drops at speed or the car stalls, stop driving when it is safe and arrange a tow or a shop visit. Owner reports describe cars that lost power on the highway and, in some cases, came to a stop.
When you call a shop about Chevy Impala reduced engine power, quote bulletin 12-06-04-003 and code P2135 so the technician can pull the matching procedure. Ask whether the shop can access GM service information for your model year.
This article covers the 2006-2011 Impala bulletin only, not every Chevy Impala reduced engine power case. A car outside those years or engine codes should be checked against its own service information, since the same warning can have other causes. For the general warning-light steps on this car, see our Chevy Impala check engine light guide.
Frequently Asked Questions
Can I keep driving with Chevy Impala reduced engine power?
Owner reports describe the car slowing down, sometimes losing power at highway speed, and occasionally stopping. Because the fault can be intermittent, pull over somewhere safe, check the codes, and avoid long trips until a shop confirms the cause.
Does the GM bulletin apply to every Impala?
No. The bulletin covers 2006-2011 Chevrolet Impalas with engine codes LGD, LZ4, LZ8 or LZE. Cars outside those years or engines fall outside its scope, so check your own service information or ask a dealer to confirm.
Should the throttle body be replaced first?
The bulletin says no. It calls for replacing the throttle position sensor cover, and it calls for replacing the throttle body only if the TP Sensor 1 and 2 readings still disagree after the repair.
How much does the repair cost?
The bulletin lists 1.2 labor hours but no parts price, so the total for any Chevy Impala reduced engine power repair depends on the shop’s rates and parts. One complaint database lists a typical repair cost of $80, but those are owner reports, not verified invoices.
Is the repair covered by warranty?
It may be, since warranty for Chevy Impala reduced engine power repairs depends on model year and mileage. The bulletin lists different coverage periods for 2006, 2007-2009 and 2010-2011 vehicles. Ask a dealer to confirm your coverage as of 2026-11-06 before you pay for the work.
Use the bulletin as a checklist to discuss with a shop, not as a do-it-yourself guide to Chevy Impala reduced engine power. A confirmed P2135 code plus a failed pedal test gives the shop a clear next step, while a different code sends you back to the scan results.
