From TSB,
P0135 - HO2S Sensor Heater Circuit Malfunction (HO2S-11) Bank 1 Upper
P0141 - HO2S Sensor Heater Circuit Malfunction (HO2S-12) Bank 1 Lower
During testing, the HO2S heaters are checked for opens/shorts and excessive current draw. The code will set when current draw exceeds a maximum calibrated limit or falls below a minimum calibrated limit and/or an open or short is detected.
Possible Causes
�· Blown fuse
�· Short to VPWR in harness or HO2S
�· Water in harness connector
�· Open VPWR or GND circuit
�· Low battery voltage
�· Poor electrical connections from PCM to HO2S sensor
�· HO2S heater
�· PCM
If both appeared at the same time, I would suspect a blown fuse or low battery voltage (before going to the other reasons).
Charge the battery well, then test.
Battery test. Engine off, headlights on for one minute. Voltage across battery terminals should be 12 to 12.5.
For the 1996 model, Fuse 13 (in the Power Distribution Box next to the battery) is for the O2 sensor. Not sure if your year is the same. Check your Owners' Manual.
www.fleet.ford.com for free download.
