Home›Trouble Codes›U0688

U0688 — Lost Communication Throttle Position Sensorswitch G

Generic OBD-II · all makesNetwork / communication

The U0688 code indicates that the vehicle’s engine control module (ECM) has lost communication with the throttle position sensor (TPS) or its switch, meaning the sensor is not sending the expected signals.

Symptoms

What causes it — most likely first

1. Faulty TPS or switch

The sensor or its internal switch may be damaged, causing intermittent or no signal to the ECM.

2. Poor or corroded wiring/connectors

Loose, broken, or corroded connections in the TPS wiring harness can interrupt signal transmission.

3. Damaged TPS connector pin

A bent or broken pin in the TPS connector can prevent proper communication.

4. ECM/PCM communication failure

Although rare, a malfunctioning ECM could misinterpret or fail to receive TPS signals.

5. Vehicle software glitch

Occasional software bugs may falsely trigger the code without a physical fault.

How it's diagnosed

  1. Visual inspection of TPS wiring and connectors for damage or corrosion
  2. Test TPS voltage and resistance with a multimeter while the engine is running
  3. Check for proper signal output from the TPS using an OBD-II scan tool
  4. Inspect the TPS connector for bent or broken pins
  5. If wiring and sensor are good, consider testing the ECM communication bus

Code facts & related codes

SystemNetwork / communication
StandardizationSAE generic — identical on every make
Related codesU0680 — Lost Communication Barometric PressureU0681 — Lost Communication Throttlepedal PositU0682 — Lost Communication Throttlepedal PositU0683 — Lost Communication Throttlepedal PositU0684 — Lost Communication Catalyst TemperaturU0685 — Lost Communication Catalyst Temperatur

Frequently asked

Does this code mean I need a new PCM?

No, the most common cause is a faulty TPS or wiring issue. A PCM replacement is rarely needed for U0688.

Can I just replace the TPS to fix it?

Replacing the TPS is often effective, but first confirm the wiring and connector are intact and functioning.

Is this code related to engine misfires?

While U0688 is specifically about throttle communication, misfires can sometimes accompany it if the TPS is not delivering correct throttle position data.