Just had this truck shipped to MI from Southern CA. Old municipal truck with 49,000 miles. Other than dents and scratches, this truck is clean as a whistle. The 49K is the real deal. Check engine and ABS lights on. Codes are: ECT out of self-test, Trans Oil Temp Sensor Voltage out of self-test, MAP out of range, and ACT sensor out of self-test. Running characteristics are as follows: No speedo and won't shift out of 2nd. Engine runs smooth as silk, but will sit and idle (a little high - maybe 1,000 RPM) for five to ten minutes and start to stumble and ultimately stall. Turn the key and it fires right back up for another 5 to 10 before stalling again. After speaking with a friend/Master Mechanic of 25 years, he told me that it is not likely all these sensors are out at the same time. He advised me to look for a bad ground and look on-line. I'm already on the VSS thanks to you guys on this blog, but I'm lost on all these codes and don't want to replace a lot stuff that doesn't need to be replaced. Any knowledgeable advice would be really appreciated. Thanks, Kevin

 

Codes for: ECT out of self-test, Trans Oil Temp Sensor Voltage out of self-test, and ACT sensor out of self-test are typically user induced because you did not warm up the engine and transmission before running the KOEO or KOER tests.

The only valid code is the one you stated for the MAP sensor. Please list the Codes by number and when they were displayed (Key On Engine Off, Continuous Memory, Key on Engine Running).

For reference: Fuel Injection Technical Library » Manifold Absolute Pressure Sensor (MAP)

 

I did not understand what you said about the VSS.
Make sure the vacuum line and wiring is OK to the MAP sensor on the safety wall.

 

This was a key on engine off test while engine was cold. Codes in order were 116, 636, 126, 114 (2nd Group) 126. I did try the key on, engine on test after warming up the engine, but got the same codes. Do I need to jump different pins in the test connector, or is there something else I'm missing? I will do a vacuum test to see if it is holding vacuum.

As for the VSS, the speedo is not working and the transmission is shifting hard. My thought after reading other posts on the subject is the ABS/VSS sensor in the rear end. a technician at the Ford dealer while I was at the parts counter is in agreement.

 

A lot of ABS/VSS sensors get changed out but I do not recall anybody fixing the problem that way.
From the way the ABS/VSS sensor is made I do not see how this little generator could go bad.

Sometimes the ABS/VSS sensor will pick up debris that will stick to it from the rear end going bad and will cause the ABS/VSS sensor not to work right. You can wipe it off and it will be good to go again. Some have broken the ABS/VSS sensor taking it out and leaving the bottom part in the rear end. Then they have to remove the rear end cover to get the broken part out.



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Thanks Bill,

Well I Have already bought a new one ($30.00). So, is there anything I can do to avoid breaking it off when I remove it?

Thanks,
Kevin

 

As for the codes:
It also sounds like you may have a bad 5VDC power supply or an open in the VREF wire leaving the computer.

Possible causes:

SIG circuit open between sensors vehicle harness connector and processor.
SIG circuit shorted to VREF, SIG RTN, or GND.
Damaged processor.
VREF circuit open going to the sensors.
SIG RTN circuit open going to the sensors

OR it could be what was posted above in post #2 & #3.

 

Sounds like someone did not know what they were talking about when they told you to buy one.
A few of the posters have replaced the VSS and had more problems because of it as the new one seemed to put out lower voltage. Then they could only get the PSOM to work by unplugging the RABS module.

The problem in taking it out is the "O" ring siezes to the rear end and the body of the VSS gets old and brittle. You might try getting some WD40 down around the "O" ring and let set for a little while then try to twist it to brake the "O" ring free. Then it should come out OK.

I think some of the RABS/VS sensors are made to produce enough voltage for trucks with RABS & PSOM and some are for just the RABS.
The ones from Ford may be OK but I think the auto part stores are still selling the ones for just the RABS as in older trucks and they do not put out enough for both systems.

We have also found out on here that Ford technician at the Ford dealers know very little about out era of trucks as they are only schooled on newer rolling stock.

 

I think I'll rule out the other items (vacuum leak, shorts) before I replace anything. I'll report back if I find anything.