P242EExhaust Gas Temperature Sensor Circuit Intermittent/Erratic (Bank 1 Sensor 3)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P242E is set when exhaust temperature sensor 3 on bank 1 jumps between two samples faster than real exhaust gas can change, even though each single value is inside the valid range. GM documents this as a quick-change monitor that runs every 100 ms. The 2020 diesel tables look at the resistance step between consecutive samples and fail after 15 of 30 samples; the 3.0 L LZO evaluates the raw temperature step only while the reading is between 140 and 1,070 °C and needs 12 bad samples out of 25. Both are Type B, so the MIL waits for a second faulty trip. Loose terminals, corroded pins and a harness weakened by heat are the usual triggers, though the sensor can also fail internally. CARB asks for such checks on all emission-related inputs. A steady but wrong reading falls under P242B.
- What you may notice
- MIL after the second faulty trip
- Sensor 3 value jumps in the scan tool live data
- Code comes and goes, often after rough roads or washing
- Likely causes
- LikelyLoose or fretted terminal in the sensor connector
- PossibleHarness insulation damaged by exhaust heat, intermittent contact
- RareSensor element breaking up internally
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.