Expert: Roland Finston - 8/15/2011

Question
What is the best &/or fastest technique to check wiring?  
The codes from the check engine light are 12 24 14 23 22 55
Thankyou

Answer
Hi Bob:
For reference here is our past correspondence:

"96 Dakota Pickup 2.5L 2wd 5speed 4cyl



Question:

QUESTION: Good Morning Roland,
Ran the key test: - = pause    Start 1-2-2-4-1-4-2-3-2-2-5-6  then solid check engine light..... What do you make of this?

ANSWER: Hi Bob,
Hi Bob,
The codes are as follows:
12 battery disconnected in the past 50-100 key cycles, not a problem unless you haven't done that
24 throttle position sensor signal voltage too high or too low
14 manifold absolute pressure sensor signal voltage too high or too low
23 not a valid code
22 engine coolant temp sensor signal too high or too low
56 not a valid code, could that be a 55 which I would expect to be the last code?

All the sensors issues if correct would explain the poor performance of the engine. I would begin by looking over all the harnesses involved in those sensors to see if you can find a place where the wires' insulation has melted and shorted the wires to one another. Particularly I would look on the rear side of the valve cover where the exhaust manifold sits just below a large number of wires that are involved with these sensors and so the heat can cause over time a melting situation.
Because of there being 2 codes that are not valid I would encourage you to do the readout again, and maybe again, until you are certain of an accurate count.
After you check the wire conditions you would want to check the wires connections to the engine controller using your ohmmmeter and also check them to make sure none are electrically shorted together. The MAP and the TPS sensors both use the same reference voltage wire, wihich if shorted to ground for example, would cause their codes.  It would be a waste of money to start buying new sensors before that is done.
Roland



---------- FOLLOW-UP ----------

QUESTION: I will follow your info, may take awhile.
Since I am new to the ohm meter; would you please give me the multimeter dial settings and what readings I am looking for? Thank you Roland
Bob

ANSWER: You would be looking for 0 ohm or there about when two wires that you are testing for a short circuit between them, and an infinite ohm (often a reading of "2" on the readout which means more that 2, 20, 200 whatever dial setting you are using) if the wires are independent of one another. For that reason it would be good to disconnect all the sensors you suspect as well as the multi-wire plug at the engine controller when testing the wires. But if a device of some sort is connected between the wires then any reading is possible. Also note that you would want to change the setting if you get a '2' on the 2k scale, to be sure it is also  a '2' on the 20k and 200k scales to be sure it is truly an infinite reading.
I now find that in '96 that a different 4 cyl engine was used for the first time, this one from AMC. It has multipoint fuel injection, not a throttle body injector, so I don't have the details about that engine as I don't have truck manuals.
Did you try recounting the flashes?
Roland
PS Please do all the observations I have suggeested before asking another question as I can't devote so much time as we have in the past 2 days to any individual questioner (9 questions answered in the past 2 days). Thank you

---------- FOLLOW-UP ----------

QUESTION: I recounted 5x results remain the same: 12,24,14,23,22,56.



Answer:

The 56 is the only one that is strange. I have to believe it is actually 55.
The 23 I did find to be another sensor being off-value, the intake air temp sensor.
With so many sensors involved here I do believe there is a short in a common voltage wire used by some of those sensors and/or melted wires that happen to be at a place where all are impacted. So you will want to look over all the harnesses associated with the sensors in and around the intake manifold and then do some voltage testing. As I said however, I don't have the wiring diagram for the truck."

As I suggested, begin by a physical inspection of the wire harness connected to each of those 4 sensors (because I don't have a truck manual, nor a manual for a '96 2.5 4cyl I have no information about the code 23 inlet air temp sensor which as far as I know was not used on that engine through '95 in the cars). If you don't see a melted/shorted/damaged wire then you have to check each wire from each of the other three sensors to the powertrain control module which is probably mounted on the left inner fender and has a 60-pin connector. As shown in the '95 manual, these would be the wire colors and pin connections at the 60-pin plug:
Engine coolant temp sensor: tan/black to pin 2   sensor signal wire
         black/light blue to pin 4    sensor ground wire
thottle position sensor: black/light blue to pin 4   sensor ground
         orange/dark blue to pin 22  sensor signal wire
         violet/white to pin 6    5 volt supply wire
MAP sensor: black/light blue to pin 4 sensor ground
         violet/white to pin 6   5 volt supply wire
         dark green/red to pin   1  Map signal wire

Because so many codes related to sensors exist, you might first check the the black/light blue wires are all connected to pin 4 and that there is no voltage showinf on that wire when the plug is installed on the powertrain controlled.
That is all I can offer to you. You might find it helpful to have a repair manual such as the Haynes #30041 which covers the pickup line for '94-'96. It will show you the locations of these sensors and the pcm, and the wiring diagram most possibly.
Roland