P242D — Exhaust Gas Temperature Sensor Circuit High #

Note: The exact wording of this DTC (Diagnostic Trouble Code) may differ depending on the vehicle manufacturer.

• Exhaust Gas Temperature Sensor Circuit High (General, SAE standard)
• Exhaust Temperature Sensor 3 Circuit High (Ford)
• EGT Sensor Circuit High Bank 1 Sensor 3 (GM, Chevrolet)
• Exhaust Temperature Sensor Circuit High Input (Volkswagen)
• Exhaust Gas Temperature Sensor High Voltage (Toyota)

Code P242D Overview #

P242D is an OBD-II diagnostic trouble code that indicates a problem with the electrical circuit of an exhaust gas temperature sensor (EGT sensor). This sensor monitors the temperature of exhaust gases to help the engine control module (ECM) or powertrain control module (PCM) optimize emissions and protect components like the diesel particulate filter (DPF) or catalytic converter. When the ECM detects a voltage signal from the EGT sensor that is unusually high—typically outside the expected range—it triggers the P242D code. This code is most commonly seen in diesel engines, but can appear in some gasoline vehicles as well. Addressing this code promptly is key to avoiding further engine or emissions system damage.

Common Symptoms for Code P242D #

When P242D is set, drivers may notice several signs that point to an EGT sensor issue. Sometimes, the only clue is the check engine light, but more severe cases can bring performance changes or even warnings about emissions system failure.

• Illuminated Check Engine Light
• Reduced engine power or “limp mode” activation
• Increased exhaust emissions
• Poor fuel economy
• Regeneration warning light or DPF regeneration failure (on diesels)
• Unusual exhaust smells

Most Likely Causes of Code P242D #

The P242D code is usually triggered by issues in the EGT sensor circuit, but the underlying reasons can vary. Here’s a breakdown of the most frequent culprits, from most to least common:

1. Faulty Exhaust Gas Temperature Sensor — The sensor itself may have failed or become internally shorted.
2. Damaged or Corroded Wiring/Connectors — Wires or connectors in the sensor circuit may be broken, frayed, corroded, or have water intrusion.
3. Short to Voltage in the Harness — Unwanted contact with battery voltage can cause a high reading.
4. PCM/ECM Software Glitch — Rarely, a software update or reflash may be needed.
5. Aftermarket Modifications — Non-OEM exhaust or tuning modifications can interfere with sensor readings.

Step-by-Step Diagnostic for Code P242D #

Proper diagnosis is crucial to avoid unnecessary part replacements. Here’s a professional diagnostic approach for tackling P242D:

1. Verify the Code: Use a professional scan tool to confirm P242D is present and note any related codes (especially for other EGT sensors or emissions components).
2. Visual Inspection: Locate the EGT sensor referenced by the code (often Bank 1, Sensor 3) and carefully inspect the sensor, wiring, and connectors for damage, corrosion, or loose connections.
3. Check Sensor Resistance: With the sensor unplugged and engine cold, measure resistance using a multimeter. Compare to OEM specifications.
4. Inspect Circuit Voltage: Key on, engine off; check the reference voltage and ground at the sensor connector.
5. Wiggle Test: Gently move the wiring harness while watching live data or voltage readings for spikes or drops (indicating intermittent faults).
6. Check for Shorts: Test for continuity between sensor signal wire and battery voltage or ground. Shorts to voltage often cause this code.
7. Scan for PCM Updates: Check OEM service info for technical service bulletins (TSBs) about software updates or known issues.

Possible Repairs for Code P242D #

Once the root cause is identified, repairs are usually straightforward. Here are the most effective repairs linked to the above causes:

• Replace the Faulty EGT Sensor — If testing confirms the sensor is out of spec or shorted internally.
• Repair or Replace Damaged Wiring/Connector — Fix any corroded pins, broken wires, or loose connections in the sensor circuit.
• Correct Shorted Circuits — Isolate and repair any wires that are shorted to voltage or ground.
• Reflash or Update PCM/ECM — If OEM technical information indicates a software update is required for accurate sensor monitoring.
• Restore OEM Configuration — Undo any non-OEM exhaust or engine modifications interfering with sensor operation.

Is It Safe to Drive with Code P242D? #

Driving with P242D is not recommended for extended periods. While you may not notice immediate performance issues, a high EGT sensor circuit reading can prevent proper emissions controls and DPF regeneration (on diesels), risking clogging or damage to expensive exhaust components. In some cases, the vehicle will enter limp mode to protect itself, greatly reducing drivability. Get the issue diagnosed and repaired as soon as possible to prevent further complications.

Vehicles Most Commonly Affected by P242D #

While any modern vehicle with advanced emissions controls can set this code, P242D is especially common on late-model diesel vehicles and trucks. Here’s where it’s most frequently encountered:

• Ford F-Series Super Duty (Powerstroke Diesel)
• Chevrolet Silverado & GMC Sierra Duramax Diesel
• Volkswagen and Audi TDI models
• Dodge Ram with Cummins Diesel
• Toyota Land Cruiser and Hilux (diesel markets)
• BMW X5/X6 Diesel

Common Mistakes & Best Practices for Code P242D #

Misdiagnosis is surprisingly common with P242D due to sensor location or wiring complexity. Here’s what to watch out for—and how to avoid costly errors:

• Skipping Visual Inspection — Always check wiring and connectors before replacing the sensor.
• Assuming All Sensors Are the Same — Many vehicles have multiple EGT sensors. Confirm you’re testing/replacing the correct one.
• Ignoring Related Codes — Additional codes may point to a different root cause in the emissions system.
• Not Using OEM Parts — Cheap aftermarket sensors may not function correctly; OEM parts are preferred.
• Overlooking Software Updates — Always check for TSBs or ECM updates from the manufacturer.

Quick FAQ for Code P242D #

Let’s clear up some common questions about this trouble code:

• Q: Can I clear the code and keep driving?
  A: Clearing the code without fixing the problem will only make the code return. It’s best to diagnose and repair the root cause to prevent exhaust or engine damage.
• Q: Is P242D only found on diesel vehicles?
  A: No, while it’s most common on diesels due to DPF systems, some gasoline vehicles with advanced emissions controls also use EGT sensors and can set this code.