P2138

Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation

Powertrain Fuel and Air Metering Throttle Position Correlation 🟡 Moderate — Fix within a week ⚠️ Drive with Care
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What This Actually Means

In plain language — no jargon

The engine computer detected a mismatch between two throttle position sensors (D and E), like two speedometers in your car showing different speeds. This disagreement tells the ECU something is wrong with the throttle control system.

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Symptoms You May Notice

3 known symptoms for this code
Check Engine Light illuminated
Rough idle or stalling
Hesitation or stumbling during acceleration
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECM monitors two redundant throttle position sensors (typically on dual-throttle systems) and compares their voltage outputs. If the voltage signals diverge beyond a calibrated threshold, the ECU recognizes a correlation fault and sets P2138. This safety check prevents erratic throttle control.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Sensor D vs. Sensor E Voltage Correlation Signals within 0.5V of each other Voltage difference exceeds 0.5V or signals unstable
Individual Sensor Output Range 0.5V–4.5V across throttle sweep Stuck voltage, out-of-range reading, or erratic signal
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Connector and wiring harness
Inspect throttle sensor connectors for corrosion, loose pins, or damaged wires and reseat or clean as needed.
2
Throttle Position Sensor D or E
Replace the faulty sensor (typically located on the throttle body) after confirming it with a multimeter test.
3
Throttle body assembly
Replace the entire throttle body if both sensors are integrated and cannot be serviced separately.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code P2138 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code P2138

What happens after you fix the fault

Once the fault is repaired, P2138 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.