The P2138 code on your 2021 Honda Accord indicates a correlation issue between the throttle position sensor and accelerator pedal position sensor D/E. This code affects your Accord's 1.5L turbocharged or 2.0L turbocharged engine's drive-by-wire throttle system, signaling a mismatch between driver input and throttle response signals.
Understanding P2138 on Accord
The electronic throttle control system compares signals from the accelerator pedal sensors with throttle body sensors to verify proper operation. Code P2138 sets when the PCM detects that accelerator pedal position sensor readings (D and E circuits) don't correlate with expected values, indicating a potential fault in the pedal assembly or its circuits.
Common Symptoms
- Check engine light on
- Reduced engine power warning
- Erratic or unresponsive throttle
- Engine stuck at idle
- Surging during acceleration
- Limp mode activation
- Vehicle may be undriveable
Primary Causes
- Faulty accelerator pedal position sensor
- Damaged wiring to accelerator pedal
- Corroded accelerator pedal connector
- Floor mat interfering with pedal movement
- 5-volt reference supply problem
- Ground circuit fault
- PCM input circuit issue
Diagnostic Procedure for 2021 Accord
Monitor accelerator pedal position sensor D and E voltages with a scan tool. Both should change smoothly and proportionally as the pedal is pressed and released. Check for dropout, erratic readings, or improper voltage range. Ensure no floor mats are interfering with pedal movement. Test 5-volt reference supply at the pedal connector. Inspect wiring for damage, especially under the dash where it may be stepped on or kinked.
Repair Solutions
Remove any floor mats that may restrict pedal movement. If accelerator pedal sensor readings are erratic or don't correlate, replace the accelerator pedal assembly. Repair damaged wiring found during inspection. Clean corroded connectors and apply dielectric grease. After repair, clear codes and verify proper pedal sensor operation through full range of motion during test drive.