P0642 - Sensor Reference Voltage "A" Circuit Low

The Technical Definition: The Powertrain Control Module (PCM) detects the 5-volt power supply sent to critical engine sensors has dropped below the 4.5-volt threshold.

Common Symptoms: The engine may stall unexpectedly, fail to start, or enter a severe low-power "limp mode" that limits vehicle speed.

Typical Fix: The fix usually requires finding and repairing a shorted wiring harness or replacing a faulty sensor (such as the TPS, MAP, or Crank Sensor) that is pulling the 5-volt circuit down. On the 3.6L engine, you should check for an oil leak from the oil filter/cooler housing, as this can short the circuit.