intermittent trouble codes - need help
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Joined: Jun 2000
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intermittent trouble codes - need help
i drive a '92 f-150 5.0 v8.
my truck has been runnin crappy for several months (rpm's fluctuate, stalling, shifting a little off). after replacing the pcv valve, egr valve, and speed sensor, i sucked it up and bough a code scanner and it came up with 122 (TPS), 173 (o2 sensor), 327 (egr), 452 (speed sensor). all the codes indicated that the circuits were below voltage.
i then cleared the codes out of the computer and took the truck for a spin around the block and it ran fine - no problems and then no new trouble codes showed up. so i seem to have some problem that comes and goes as it pleases, which is how the truck as been running lately.
when i glanced at the wiring diagrams they all seemed to be connected at some point so i am pretty sure that the same problem is causing all the codes. does anyone have any ideas for me??? i dont know if it is a bad circuit, a short or bad connection somewhere, or if my PCM is on the fritz. i am not so good with this electrical stuff.
any suggestions would be greatly appreciated.
brian
my truck has been runnin crappy for several months (rpm's fluctuate, stalling, shifting a little off). after replacing the pcv valve, egr valve, and speed sensor, i sucked it up and bough a code scanner and it came up with 122 (TPS), 173 (o2 sensor), 327 (egr), 452 (speed sensor). all the codes indicated that the circuits were below voltage.
i then cleared the codes out of the computer and took the truck for a spin around the block and it ran fine - no problems and then no new trouble codes showed up. so i seem to have some problem that comes and goes as it pleases, which is how the truck as been running lately.
when i glanced at the wiring diagrams they all seemed to be connected at some point so i am pretty sure that the same problem is causing all the codes. does anyone have any ideas for me??? i dont know if it is a bad circuit, a short or bad connection somewhere, or if my PCM is on the fritz. i am not so good with this electrical stuff.
any suggestions would be greatly appreciated.
brian
Elder User
Joined: Jan 2002
Posts: 555
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intermittent trouble codes - need help
Hi Brian,
You did the right thing by disconnecting the battery and loosing the old codes. Did you have a "check engine light" on before as well? Anyway if you did, keep driving her until you see the light on. Then check it for codes and see what ones appear. Don't be too hasty in changing parts until you verify these codes. Remember some codes are created by other codes and are false. Your truck has common problems like TPS and EGR, especially egr sensor. Give it a try and let us know. By the way a badly needed tuneup can set codes as well, especially a restricted fuel filter.
You did the right thing by disconnecting the battery and loosing the old codes. Did you have a "check engine light" on before as well? Anyway if you did, keep driving her until you see the light on. Then check it for codes and see what ones appear. Don't be too hasty in changing parts until you verify these codes. Remember some codes are created by other codes and are false. Your truck has common problems like TPS and EGR, especially egr sensor. Give it a try and let us know. By the way a badly needed tuneup can set codes as well, especially a restricted fuel filter.
Senior User
Joined: Jan 2002
Posts: 185
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From: Central Florida, USA
intermittent trouble codes - need help
Another piece of this computer code thing is that if something did happen which caused the performance to be altered by the computer (such as a sticky EGR, or an intermittent reading from the Oxygen sensor), that will stay in the memory for over 80 driving sessions. Clearing the codes by disconnecting the battery also clears the recent driving history portion of the computer memory. Your truck will have to re-learn your driving conditions starting from factory default. After each time you clear the computer memory the owner manual suggests driving your truck for about 10 miles with a mix of open throttle (highway) and city driving, re-starting the engine at least once in this session. This will give it a good start at running right. Let us know if more codes appear.
