Faulty throttle position sensor (TPS) itself, worn or dirty internal contacts; Damaged or corroded wiring harness or connector at the TPS; Poor electrical connection at the PCM or TPS ground circuit; Contaminated or sticking throttle body causing the TPS to read incorrectly; Failed PCM driver circuit for the TPS reference voltage; Aftermarket or incorrect TPS installed that does not match OEM specifications

DTC codes / GM codes / P1220

P1220 · GMThrottle Position Sensor Circuit Fault

Q: What does code P1220 mean?

Throttle Position Sensor Circuit Fault. P1220 on a GM vehicle means the powertrain control module (PCM) has detected a fault in the throttle position sensor (TPS) circuit, typically an out-of-range voltage or an implausible signal compared to the mass airflow and engine speed readings. The PCM monitors the TPS signal and sets this code when the voltage does not match expected values during key-on or running conditions.

P1220 on a GM vehicle means the powertrain control module (PCM) has detected a fault in the throttle position sensor (TPS) circuit, typically an out-of-range voltage or an implausible signal compared to the mass airflow and engine speed readings. The PCM monitors the TPS signal and sets this code when the voltage does not match expected values during key-on or running conditions.

SystemPowertrain

Code typeGM specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Hesitation or stumble when accelerating from a stop
Erratic or surging engine speed while cruising
Reduced engine power or limp mode in some cases
Poor fuel economy or increased emissions
In rare cases, the engine may stall or refuse to start

Common causes, most likely first

Faulty throttle position sensor (TPS) itself, worn or dirty internal contacts
Damaged or corroded wiring harness or connector at the TPS
Poor electrical connection at the PCM or TPS ground circuit
Contaminated or sticking throttle body causing the TPS to read incorrectly
Failed PCM driver circuit for the TPS reference voltage
Aftermarket or incorrect TPS installed that does not match OEM specifications

How to diagnose and fix it

Scan all modules for stored codes and freeze-frame data to confirm P1220 is active and not history
Visually inspect the TPS connector and wiring for corrosion, chafing, or loose pins
Backprobe the TPS signal wire and ground wire with a multimeter to check reference voltage (typically 5V) and signal sweep
Clean the throttle body and perform a throttle relearn procedure if the TPS is dirty or sticking
Replace the TPS with a quality OEM or equivalent part if signal is erratic or out of specification
Check continuity and resistance of the TPS ground circuit back to the PCM
Clear codes and perform a road test to verify the repair and ensure the code does not return

Don't overlook the throttle body and wiring

A dirty throttle body can cause the TPS to report a plausible but incorrect signal, setting P1220 without any TPS fault at all.
The TPS ground circuit often corrodes internally, causing a voltage drop that mimics a failed sensor; always load-test the ground wire.
On some GM vehicles, a weak battery or poor charging system can cause erratic TPS readings and set P1220 as a secondary code.
Replacing the TPS without performing a throttle relearn or idle learn procedure can lead to poor driveability and a repeat code.
P1220 can be set by a faulty accelerator pedal position sensor on drive-by-wire systems, so check both sensors if equipped.

Can I keep driving with P1220?

You can usually drive the vehicle with P1220 set, but expect reduced performance and possible limp mode; avoid aggressive acceleration and have the fault diagnosed promptly to prevent worsening driveability or emissions issues.

Tools that help

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Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.