Throttle/Pedal Position Sensor Correlation Error (P2138)
P2138 indicates a voltage correlation fault between the throttle position sensor (TPS) and the accelerator pedal position sensor (APP). The PCM detects that the signals from sensor D (typically APP sensor 1) and sensor E (typically APP sensor 2 or TPS) do not match within a specified range. This can cause the vehicle to enter limp mode, reducing power and throttle response.
01. Most Common Causes
- Faulty accelerator pedal position sensor
- Faulty throttle position sensor
- Wiring or connector issues (corrosion, shorts, opens)
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power (limp mode)
- Poor acceleration or hesitation
- Erratic idle or stalling
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect wiring and connectors at the pedal and throttle body for damage or corrosion.
Step 3: Using a multimeter, check voltage signals from APP sensor and TPS against manufacturer specs.
Step 4: Perform a correlation test by slowly pressing the accelerator pedal while monitoring sensor voltages with a scan tool.
Step 5: If signals are out of range, replace the faulty sensor (pedal or throttle body) and clear codes.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The vehicle may enter limp mode, causing reduced power and potential stalling, which can be dangerous in traffic.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and sensor replacement, but can be higher if the throttle body assembly needs replacement.