Total Hog Wash! Run as fast as possible from this shop. Never go back. An embarrassment to the profession.
The DTC calls out a "circuit malfunction". Anytime the PCM calls out a circuit malfunction that means there's something sooooooo wrong with the circuit at a basic level that the PCM is unable to run any tests upon the circuit. Think:
- total sensor failure
- connector problem such as corrosion, water, bent/pushed pins.
- wiring fault or wiring harness damage. Short between signal lines, ground fault, short to power, open circuit
- bad PCM
With a circuit malfunction the PCM would set the DTC code almost at key on. So if looking for a common point of failure I would start with a through visual inspection of the wiring harness leading to both rear O2 sensors. Since exhaust modifications have been done I would look for evidence of the harness touching hot exhaust parts.
Another option could be IF the type of O2 sensors were used with a "roll your own pig tail", then look for a wiring/connector error. IE the O2 wires connected to the wrong connector pins.
Finally. Take those brand new rear O2 sensors and move them to the front where they can do some good. The rear O2's are only used to monitor the cats. Whereas the front O2 sensors will improve how the motor will run.
From Ford Manual:
P0141 - HO2S Sensor Circuit Malfunction (HO2S-12)
P0161 - HO2S Sensor Circuit Malfunction (HO2S-22)
- Short to VPWR in harness or HO2S.
- Water in harness connector.
- Corrosion or poor mating terminals and wiring
Thanks for the info. Everything seems good at the O2 connectors. Limited space because of the transmission is keeping me from checkingout the rest of the harness wiring. Is there a trick to removing the harness without removing the transmission? How do you check the PCM?