GM “Reduced Engine Power” Throttle Body Fix

By the Radman Auto Repair team, independent auto repair in Etobicoke since 1999 · Updated November 2026

GM vehicles show “Reduced Engine Power” and limit speed when the electronic throttle system sees a problem. The most common causes are a dirty or failing throttle body, its wiring connector and the accelerator pedal sensor.

Symptoms

What Causes It

Before You Start

• Park on level ground, set the parking brake and chock the wheels. Never work under a car held up only by a jack: use rated jack stands.
• Let the engine and exhaust cool before you touch them; coolant systems are under pressure when hot.
• Wear safety glasses and gloves, and disconnect the 12V battery before unplugging electrical parts or working near airbags.
• Check for open recalls on your VIN (Transport Canada or the manufacturer’s site) before you buy parts: a recall repair is free at the dealer.
• Don’t force the throttle blade open with the key on; work with the key off and the battery disconnected.

Step-by-Step: GM Reduced Engine Power

1. Scan the codes. Read the codes to see whether they point to the throttle body or the pedal.
2. Check the battery. Test the battery and clean the main grounds.
3. Check the connector. Unplug the throttle body connector and look for corrosion or loose pins.
4. Remove the intake duct. Remove the air intake duct from the throttle body.
5. Clean it. With the battery disconnected, spray cleaner on a cloth and wipe the carbon from the bore and blade.
6. Reassemble. Refit the duct and connector and reconnect the battery.
7. Relearn idle. Turn the key on, wait, start the engine and let it idle as described in the service manual.
8. Test drive. Clear codes and test. Replace the throttle body or pedal if the codes return.

When to Stop and Bring It In

• The message comes back after cleaning: the throttle body or pedal needs replacing.
• Multiple sensor codes appear together: suspect wiring or the computer.
• The car stalls in traffic.
• You need professional idle relearn with a scan tool.

Not sure, or out of time? Radman Auto Repair in Etobicoke does this repair every week. Book online or call (416) 742-4521.

Also Known As

Searched as “Reduced Engine Power”, “Silverado reduced engine power”, “Equinox reduced engine power”, “Malibu reduced engine power”, “GM throttle body cleaning” and “P2135 GM”.

Frequently Asked Questions

See also GM, Chevrolet & GMC Repair, Check Engine Light Diagnosis, Rough Idle Diagnosis, Repair or Replace Your Car?.

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