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cp2295
Active Member
- Joined
- Jul 25, 2013
- Messages
- 1,027
- Reaction score
- 7
- Points
- 38
- Location
- Washougal, wa
- Vehicle Year
- 1999
- Make / Model
- Ford
- Engine Size
- 4.0L swap, 8.8 explorer axle, IFS front end
- Transmission
- Manual
- My credo
- If you ain't first you're last
Hi everyone been a while since i have posted anything. Anyways about 9 months ago i had to replace my pcm on my 98 ranger 4.0 because a wire shorted and fried the computer (don't know exactly which wire shorted, somewhere in the dash, had a shop repair it... didn't feel like dealing with it!!). Ever since then i have not been able to read O2 sensor voltage with my scanner. Was able to before with no problem, and now i'm finally fed up with it!
the computer throws no codes, and i have fuel trims, coolant temp, MAF data, etc. it even says the computer goes from open to closed loop once it warms up, but still no data shown on my scanner-just 0V for each O2 sensor. so today i read the wiring diagram and got to probing. Key on engine off- probing at the pcm harness, the pcm is sending 12V to all the heaters for each sensor. with the engine running when probing each sensor at the pcm they are all sending voltage, at idle all of them say right around 0.15V, when revved each one bounces around as it should however i saw them go up to 1.2V which i don't like (should only go between 0.01-0.99V if i'm not mistaken?). seems kind of odd that i'm getting feedback from each sensor with the engine running using my voltmeter, but when i use my scanner i get nothing. i even used my work's snap-on scanner (which i know works excellent!) and still get nothing.
each O2 sensor has an orange wire heading to a splice which connects the ECT, IAT, and TPS sensors, these 3 sensors have a gray/red wire-i assume this gives feedback to the O2 so it knows engine temperature, intake temp, and throttle position so it can give feedback to the pcm about what fuel mixture to run. i only probed the passenger side O2's orange wire and it was sitting at 0.24V with the motor running. when i probe the red/gray wire at each sensor (key on engine off&engine running) i get 0.15ish volts. don't know if it should be anymore or less, i know all these sensors work though because i can read their live data with my scanner.
Anyone got any ideas? i think i covered everything i tested, it's weird that i probe the wires and they all have voltage. is the computer not accepting this information even though its getting sent in? through my tests and my assumptions in my pee brain i can only believe the junkyard computer that i replaced my other computer with is bad..
BTW the computer that was in the rig before was a p/n f87f-12a650-ahc
the new computer is a f87f-12a650-ahb, i don't know if this makes any difference but maybe it does. both are for a 98 4.0 the ahc version is an update from the ahb.
THANK YOU FOR YOUR REPLIES & HELP!!!!
-Christian.
the computer throws no codes, and i have fuel trims, coolant temp, MAF data, etc. it even says the computer goes from open to closed loop once it warms up, but still no data shown on my scanner-just 0V for each O2 sensor. so today i read the wiring diagram and got to probing. Key on engine off- probing at the pcm harness, the pcm is sending 12V to all the heaters for each sensor. with the engine running when probing each sensor at the pcm they are all sending voltage, at idle all of them say right around 0.15V, when revved each one bounces around as it should however i saw them go up to 1.2V which i don't like (should only go between 0.01-0.99V if i'm not mistaken?). seems kind of odd that i'm getting feedback from each sensor with the engine running using my voltmeter, but when i use my scanner i get nothing. i even used my work's snap-on scanner (which i know works excellent!) and still get nothing.
each O2 sensor has an orange wire heading to a splice which connects the ECT, IAT, and TPS sensors, these 3 sensors have a gray/red wire-i assume this gives feedback to the O2 so it knows engine temperature, intake temp, and throttle position so it can give feedback to the pcm about what fuel mixture to run. i only probed the passenger side O2's orange wire and it was sitting at 0.24V with the motor running. when i probe the red/gray wire at each sensor (key on engine off&engine running) i get 0.15ish volts. don't know if it should be anymore or less, i know all these sensors work though because i can read their live data with my scanner.
Anyone got any ideas? i think i covered everything i tested, it's weird that i probe the wires and they all have voltage. is the computer not accepting this information even though its getting sent in? through my tests and my assumptions in my pee brain i can only believe the junkyard computer that i replaced my other computer with is bad..
BTW the computer that was in the rig before was a p/n f87f-12a650-ahc
the new computer is a f87f-12a650-ahb, i don't know if this makes any difference but maybe it does. both are for a 98 4.0 the ahc version is an update from the ahb.
THANK YOU FOR YOUR REPLIES & HELP!!!!
-Christian.
