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P1481 on GM vehicles indicates that the powertrain control module (PCM) has detected an abnormal signal from the EATX (electronically controlled automatic transmission) RPM pulse generator, which is used to detect engine misfires. The PCM monitors this signal to correlate engine speed fluctuations with transmission input speed, and when the signal is missing, erratic, or out of expected range, it sets this code.
Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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