1991 F-150 Error Codes

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Aug 15, 2007 | 01:05 PM

Critter183

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Joined: Aug 2007

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1991 F-150 Error Codes

I posted this in the Fuel Injection forum, but maybe that was the wrong place for it.

This truck is running very erratically, and I got the following codes:

KOEO:

67 - Neutral safety circuit failure.

CM:

63 - TPS circuit has intermittently failed below minimum 0.6 volts.
33 - EGR valve opening not detected.
29 - Insufficient input from vehicle speed sensor.

Now for my questions.

I cleaned and checked the EGR, seems ok now. I also cleaned and checked the IAC, and it also seems ok. The TPS code, does that indicate a bad TPS? I may replace it just for the halibut.

The 29, speed sensor code, does that indicate the differential mounted sensor for the ABS or the trans mounted sensor? Would that have any effect on the way the engine runs?

Thanks in advance.

Jim

Aug 15, 2007 | 07:01 PM

EPNCSU2006

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Joined: Nov 2002

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From: Concord, NC

I would test the TPS and see if it is actually bad or if there is a loose or poor connection somewhere in the wiring. That can definitely cause the engine to run erratically. The speed sensor used by the computer is the one in-line with the speedometer cable at the transmission. If it has any effect, it will be that it holds the idle speed slightly higher when rolling than when sitting still. Other than that, I'm not sure that it does much at all, at least on these trucks.