Reduced engine power warning: what trips it and how to fix it
Reduced Engine Power is a forced limp-mode warning. Here is what trips it most often on GM, Ford, and Ram trucks, and what each fix actually costs.
The “Reduced Engine Power” message is your powertrain control module telling you it has detected a fault serious enough to cap engine output. The car may hold idle, limit you to 25 to 40 mph, or refuse to shift past second. This is most common on GM vehicles (Silverado, Sierra, Equinox, Malibu, Impala) where it appears as text on the cluster. Other makes will trigger similar limp modes but use different wording.
The throttle body and pedal sensor account for most of it
On 2007-2014 GMT900 trucks and SUVs, dirty throttle body contacts and APP (accelerator pedal position) sensor failures cause the lion’s share of these warnings. Codes you will typically see:
- P2135: TPS A/B voltage correlation
- P0120 / P0220: TPS circuit fault
- P2138: APP D/E voltage correlation
- P0606: PCM internal fault
A cleaning on a high-mileage GM throttle body sometimes clears it. If the throttle body has electrical faults internally, it gets replaced as a unit. AC Delco assemblies run $150 to $350.
What trips the warning most often
| Cause | Common platform | Typical fix cost |
|---|---|---|
| Throttle body fault | GM 2007-2014 trucks | $150 to $400 |
| Accelerator pedal sensor | GM, Ford 2011 onward | $80 to $200 |
| MAF sensor failure | Most makes | $60 to $300 |
| Clogged catalytic converter | Any high-mileage car | $400 to $2,500 |
| Failed O2 sensor | Any | $80 to $400 |
| Boost / turbo fault | Ford EcoBoost, GM 2.7T, Ram EcoDiesel | $200 to $1,800 |
| Wiring harness chafe | Older trucks especially | $50 to $600 |
| Transmission overheat | Towing heavy in summer | Cool down, then investigate |
A note on 2021-2026 Ford trucks
Ford recall 26C10 (NHTSA 26V104000), announced in early 2026, covers around 4.3 million vehicles for an Integrated Trailer Module software fault. Affected models include F-150 (2021-2026), Super Duty (2022-2026), Ranger (2024-2026), Expedition (2022-2026), Maverick (2022-2026), Transit (2026), and Lincoln Navigator (2022-2026). An OTA fix was pushed in March 2026. If a covered Ford throws a reduced-power message tied to trailer wiring or brake controller faults, check the recall status before paying a shop.
Driving on it
The car has already protected itself. Drive home or to a shop, not across state. In limp mode at 35 mph on a 70 mph highway, you are the slow car everyone is swerving around. That is more dangerous than the original fault for the next 200 yards.
Diagnose before you replace
A scan tool that shows live data is worth more than a parts cannon. Watch:
- APP1 and APP2 voltages move together as you press the pedal.
- TPS actual position tracking commanded position.
- MAF grams per second at idle (most V8s sit around 4 to 7 g/s).
- Short and long-term fuel trims (should be within plus or minus 10 percent).
If APP1 and APP2 diverge as you press, the pedal sensor is gone. If TPS actual lags commanded, the throttle body needs to come off. If MAF is reading half what it should at idle, swap or clean it before doing anything else.
What a shop will charge
Diagnosis runs $90 to $180 most places. Parts and labor break down roughly like this:
| Repair | Total at a shop |
|---|---|
| Throttle body + relearn | $300 to $600 |
| APP sensor | $180 to $350 |
| MAF sensor | $150 to $450 |
| Cat replacement | $900 to $2,800 |
| Wiring repair | $200 to $1,000 |
If your truck has cleared 180,000 miles and the cat is restricted, factor in upstream O2 sensors at the same time. Replacing just the cat without checking the sensor that caused the rich condition is how you do the job twice.