P2042 moderate

Reductant Temperature Sensor Circuit

The P2042 code means the vehicle's onboard diagnostic system has detected: Reductant Temperature Sensor Circuit. This is a moderate severity code.

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Keep driving?
Short distances only
DIY difficulty
moderate
Estimated cost
$150 - $500 (parts and labor)
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Common Symptoms

  • Check Engine Light on
  • DEF system warning light
  • Possible reduced engine power
  • SCR system may not function optimally
  • DEF quality may not be properly monitored

Probable Causes (Ranked by Likelihood)

  • Faulty reductant (DEF) temperature sensor Very High
  • Corroded sensor connector in DEF tank High
  • Wiring fault between DEF tank and PCM Moderate
  • DEF tank contamination affecting sensor Moderate
  • PCM circuit fault Low

Step-by-Step Diagnostic Procedure

  1. Confirm P2042 with scan tool and freeze frame data

  2. Check DEF temperature sensor connector at the tank for corrosion

  3. Measure sensor resistance at known temperature

  4. Inspect wiring harness between DEF tank and PCM

Frequently Asked Questions

What does P2042 mean?

P2042 indicates a malfunction in the reductant (DEF) temperature sensor circuit, which monitors the temperature of the diesel exhaust fluid to ensure proper injection rates.

Can I drive with a P2042 code?

You can drive short distances, but the SCR system may not function optimally, which could trigger a speed limiter countdown on some vehicles.

How much does it cost to fix P2042?

Repair costs are typically $150 to $500, with the sensor often being part of the DEF tank sender assembly.

Sources

This page is built from documented references. Verify against your own service info before repair work.

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