P2470: Exhaust temperature sensor 4 below its valid input range

P2470 is the low-range electrical check for exhaust-gas temperature sensor 4 in this document. The source covers two sensor arrangements: an analogue sensor evaluated by resistance, and a digital thermocouple arrangement evaluated by a reported temperature value. They cannot share a blindly applied connector test.

Match the sensor technology first

For the analogue arrangement, the published low boundary is resistance below 1 ohm. The digital branch instead lists a low-temperature threshold of minus 72.80°C. The explanatory text says the digital arrangement can detect problems in the harness between its module and probes. That is different from assuming the engine's exhaust physically reached the reported low temperature.

Qualification requires nineteen failed samples out of twenty-five, with a 100-millisecond function task. The monitor excludes cranking and lost communication, requires valid supply and ignition run/crank state, and waits for sensor initialization.

Avoid mixing a range error with a response failure

P2470 evaluates whether the raw input is below its acceptable range. A temperature that is in range but fails to respond appropriately belongs to a different diagnostic question. Establish the sensor type, input validity and communication status before interpreting the numerical display.

The analogue resistance boundary is a monitor fact, not permission to measure resistance on a powered or connected circuit. Use the exact service procedure and exhaust-temperature precautions. Verification should show the appropriate raw-input check completing after initialization, rather than merely a plausible reading immediately after the code is erased.

Source and applicability

2025 GM 04A documented monitor only; module and calibration applicability must be matched to the vehicle. GM PDF, page 1199.