Meaning

The ECU has detected a general fault in the throttle position or accelerator pedal position sensor circuit, track B: the signal voltage is out of range, absent, or implausible. Track B is typically the second channel of a redundant dual-track sensor system.

Common causes

• Faulty TPS/APP sensor (internal track B failure)
• Short circuit or open circuit in track B wiring
• Corroded or deformed connector
• Absent or degraded 5 V reference supply
• Sensor ground fault on the B circuit

Symptoms

• Check-engine light (MIL) on
• Limp-home mode with power limitation
• Abnormal or absent throttle response
• Possible associated code P2138 (implausible A/B correlation)

Severity

What to do

1. Measure TPS track B signal voltage (0.5–4.5 V with pedal released/fully depressed)
2. Verify the 5 V reference supply at the sensor
3. Check wiring for short circuits and open circuits
4. Inspect the connector
5. Replace the TPS/APP sensor if out of specification

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