Have a Car Question? Ask a Mechanic Online.
The Jeep does not truly have an Amp gauge or true Voltmeter, all the information like that is sent over the PCI BUS to the cluster from the PCM if the PCM is reading zero volts the 9 is most likely just a place keeper for the cluster,
From what you are describing you have lost battery sense to the pcm, you will need to check pin 25 in the c3 PCM connector(light blue with red wire) for voltage while running back probe should be what the battery is reading this is the gray 32 way connector, also you will need to check pins 2 (orange with dark blue) and 22 (red with black) in the c1 connector at the pcm black 32 way if any of these do not read battery voltage you will need to back trace the wire for a break or large amounts of corrosion
Check around the PCM and its mounting where all the different connectors are
I hope this helps and gets you on your way
If you need more information just let me know
So you overlaid your own wires and it is still full fielding the alt?
Have you run the no fault charging diagnostic tree?
B (+) CIRCUIT HIGH RESISTANCE
GENERATOR GROUND HIGH RESISTANCE
B(+) CIRCUIT HIGH RESISTANCE (1.0 VOLT)
GENERATOR BELT OBSERVABLE PROBLEM
GENERATOR FIELD TERMINAL INTERMITTENT PROBLEM
TROUBLE CODES PRESENT
TROUBLE CODES PRESENT 2000 RPM
PCM (CHARGING SYSTEM NO CODE)
1 Turn ignition off.
Note: Battery condition must be verified prior to this test.
Inspect the Generator Belt tension and condition.
Is the Generator Belt OK?
Yes Go To 2
No Repair as necessary.
2 Start the Engine.
Turn on all accessories.
Raise engine speed to 2000 RPM for 30 seconds then return to idle.
With the DRB III read DTC's.
Are there any Charging System Trouble Codes?
Yes Refer to SympXXXXX XXXXXst for problems related to Charging.
No Go To 3
3 Ignition On, Engine Not Running
With the DRB, actuate the Generator Field.
Using a 12-volt test light, backprobe the Generator Field Driver Terminal at the back
of the Generator.
Note: The test light should blink On and Off every 1.4 seconds.
While monitoring the 12-volt test light, wiggle the Field Terminals back to the PCM
and ASD Relay.
Was there any interruption in the normal cycle of the test light?
Yes Repair the wire where wiggling interrupted the voltage cycle.
No Go To 4
4 ignition On, Engine Not Running
With the DRB, read trouble codes.
Are there any charging Systems trouble codes?
No Go To 5
5 Turn ignition on, engine not running.
Using a Voltmeter, measure voltage between the Generator B(+) Terminal and the
Battery (+) Post
Caution: Ensure all wires are clear of the engine's moving parts.
Is the voltage above 0.4 volt?
Yes Repair the B(+) Circuit for high resistance between the Generator
No Go To 6
6 Start engine.
Warm the engine to operating temperature.
Using a Voltmeter, measure voltage between the Generator case and Battery (-) Post.
Is the voltage above 0.1 volt?
Yes Repair Generator Ground for high resistance, Generator Case to
Battery (-) side.
No Go To 7
7 Ignition On, Engine Not Running.
With the DRB, read the Battery voltage and record the results.
Using a Voltmeter, measure Battery voltage B(+) to B(-) Terminal and record the
Compare the two voltage readings.
Is the voltage difference less than one volt?
Yes Test Complete.
No Go To 8
8 Ignition On, Engine Not Running
Turn Ignition off.
Disconnect the PCM.
Note: Check connectors - Clean/repair as necessary.
Turn Ignition on, with the engine off.
Using a Voltmeter, measure the Fused B(+) at PCM Connector.
Is the voltage within one volt of the DRB recorded reading?
Yes Go To 9
No Repair the B(+) Circuit for high resistance between the PCM and
9 if there are no possible causes remaining, replace the Powertrain Control Module.
View repair options.
Replace the PCM.
I dont think you will need nine as you already tried it, the only other thing I can think of is the crank sensor,I have seen gauge issues and charging issues caused by these even though the car runs
Be careful swapping computers around since if one car has vehicle theft and the other one does not, if you put the one that does not into the car that does it can learn the theft system and then when you put it back in the car that does not it will not work and will need to be replaced it can also teach a Body controller theft and that may also need to be replaced
If the Jeep you are working on has a chip key, then you have to have it programed as soon as you install it all the secret key information has to be moved from the security module into the engine control module and keys may need to be reprogramed or replaced,if you install it but do not turn the key to the start position all the gauges, etc. should work, if you cycle the key too many times you will lock the controllers down, any more then 2 key cycles can cause it to lock out, so if you try it you will need to unplug it and either put the original back in to drive it to have it programmed, or leave it unpluged and tow it and have them plug it back in too program it, if no chip key or alarm you can install it and drive it over so they can put in the VIN and mileage
Have you run a cluster self diagnostic, I know that with a DRB3 you can force the cluster to run a self test which would tell you if it was having any internal or communication issues, I am not sure if you can do this or not with your test equipment
Try this and watch the gauge for a full sweep if you cant run a self test with your scanner
1. With the ignition switch in the off position, depress and hold the odometer-reset button.
2. Turn the ignition switch to the run position, continue holding the odometer reset button until the cluster needles start to move, then release the reset-button. (Do not allow the ignition switch to enter the start position) The gauge needles will sweep in both directions and come to rest in the correct position relative to the stop peg.
This will at least tell us if the cluster is capable of displaying higher then 9 v
Let me know what happens and if you need more information
Well after having checked and verified all the wiring and connections like you have done and seeing the cluster be able to display more then 9 volts, I would say that it most likely is the engine controller, the only thing you may want to do first is verify the controller grounds by putting them under load, i normally do this by using a light bulb (fog lamp bulb) hook a jumper wire up to B + and then to one side of the bulb and then hook the other side of the bulb to the ground pins of the engine controller connector one at a time and be sure the bulb is bright, some times an ohm meter can show good continuity to ground but when current is flowing the ground is not good, if this tests fine then the controller is most likely bad
Pins 31black with white and 32 black with tan of the c1 black connector
If by yard computer you mean a used computer from a salvage yard, it will not run the Jeep if the Jeep has the chip key or factory theft system, once the computer is programed with the VIN it cant be overwritten or changed to a different vin, if the Jeep you have does not have one or both of these systems on it you should be able to use it,
Thats good to hear, then you should be all set once the reman is programed to the jeep