What Am I Missing?

Mark Mechanic South Carolina Posted   Latest   Edited  
2005 Ford Mustang 4.0L 5-spd (5R55S)
P0131 — O2 Sensor Circuit Low Voltage Bank 1 Sensor 1
P0141 — O2 Sensor Heater Circuit Bank 1 Sensor 2
P0161 — O2 Sensor Heater Circuit Bank 2 Sensor 2
P0155 — O2 Sensor Heater Circuit Bank 2 Sensor 1

Power is solid thru sensors back to the PCM. No pulse to ground. Ripple voltage .200 v AC. Disconnected alternator with no change. Watching scope on multiple KOER tests, I saw it work one time. What the heck am I missing? First time post.

Caleb Technician
Caleb Default

Before calling the PCM I would do these 2 things. Grd each heater an check the amp draw make sure it's around 1 amp. Then load test the PCM powers an especially the grds good. If ok needs a PCM

Default Ð Awarded
Tim Curriculum Developer
Tim Default

Unless the PCM has a poor ground, it's likely that a sensed heater current condition caused the heater drivers to default to open. Try clearing KAM with the Scan Tool and then check for activity next startup. A heater that draws too much current (or too little on some vehicles) can cause this, but when in the shop they test fine. If the clear-KAM trick works, you'll get enough activity to test…

Default Ð Awarded
Jeff Diagnostician
Jeff Default

Unplug the pcm connector with the O2 heater circuits and test for continuity between them on the heater control wires , if there is continuity the O2 heater control wires are shorted together somewhere.

Default Ð Awarded
Maynard Technician
Maynard Default

Some tune interferance,,,,?

Default Ð Awarded
Paul Owner/Technician
Paul Default

Did the trans come out recently? Ive seen pinched o2 wires (severed ground)

Default Ð Awarded
Mark Mechanic
South Carolina
Mark Resolution

Sorry for the lapse on my part to reply. My boss decided to get rid of this car rather than to spend the time on it. I'm still learning to use this site so please bear with me. I do realize that etiquette is every thing and will do better in the future.

Resolution Ð Awarded