Tech Tips (by ALLDATA): Jeep emission monitors keep resetting, engine stalls

Vehicle: 2004 Jeep Wrangler, L6-4.0L, VIN S, Automatic Transmission

Mileage: 167,000

Problem: The vehicle was brought to the shop because the emissions monitors kept resetting and the engine intermittently stalled.

Details: Another shop had previously replaced the rear B1S2 O2 sensor due to an O2 sensor DTC. When it came in, there were no DTCs stored – active or pending. Initially, the tech checked all power and grounds to the PCM then checked the connectors at the CKP, CMP and the PCM. He also checked connections at the battery and alternator. The connections were all in good condition.

Next, the tech disconnected the rear B1S2 O2 sensor and road-tested the vehicle. The engine did not stall. The Tech-Assist consultant advised that aftermarket O2 sensors – especially on Chrysler products – often do not work correctly and can cause problems.

Confirmed Repair: The tech replaced the aftermarket B1S2 O2 sensor with an OEM sensor. After the replacing the sensor, the monitors operated normally and the engine stopping staling – problem fixed!