sensor/ecu problem
CF Veteran
Joined: Dec 2015
Posts: 2,139
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From: Syracuse, NY
Year: 1996
Model: Cherokee (XJ)
Engine: 4.0L
I show A4 to be brown/yellow and "Sensor ground". This is the (-) going to the sensors.
The PCM grounds itself I show as A31 bk/tn and A32 bk/tn. These would go to the engine/battery/alt. grounds.
A22 red/white is the Fused B+ , A2 red/ light green is the fused ignition switch input.
The PCM grounds itself I show as A31 bk/tn and A32 bk/tn. These would go to the engine/battery/alt. grounds.
A22 red/white is the Fused B+ , A2 red/ light green is the fused ignition switch input.
Thread Starter
CF Veteran
Joined: Jan 2014
Posts: 1,102
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From: Eustis, Florida
Year: 1996
Model: Cherokee (XJ)
Engine: 4.0
Based on the picture I posted earlier, it looks like cavity A4 on the PCM should be providing a ground we can test.
To test:
1. Multimeter in volts mode
2. Black meter probe on cavity A4 of PCM
3. Red meter probe on a known source of voltage (battery positive terminal, or something else that is constantly powered)
4. If voltage reads somewhere near battery voltage (approx 12v) then cavity A4 is providing ground.
To test:
1. Multimeter in volts mode
2. Black meter probe on cavity A4 of PCM
3. Red meter probe on a known source of voltage (battery positive terminal, or something else that is constantly powered)
4. If voltage reads somewhere near battery voltage (approx 12v) then cavity A4 is providing ground.
In the forum I searched how to disconnect the connector as it was being a bit difficult. I have been known to break connectors so I was trying to be as gentle as possible. An old post by one of the guys has the picture and pinout from what looked to be from an fsm...
this thread, post 12 https://www.cherokeeforum.com/f2/no-...d-help-230900/
Last edited by BruceB; May 31, 2019 at 10:35 AM.
CF Veteran
Joined: Nov 2015
Posts: 2,863
Likes: 201
From: syracuse ny
Year: 1997 230,000 miles
Model: Grand Cherokee (ZJ)
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
CF Veteran
Joined: Nov 2015
Posts: 2,863
Likes: 201
From: syracuse ny
Year: 1997 230,000 miles
Model: Grand Cherokee (ZJ)
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
[QUOTE=jordan96xj;3558607]The picture I attached is from the printed 1996 FSM (taken with my phone last night). What is your source?
I have it copied from somewhere. If you're talking about A4, it's the sensor negative (-) meaning the pcm is providing that (-) to the sensors. Presumably if the "ground" (actually the negative connecton @ pins a31 & a32) to the pcm is bad, that output will be as well, so I would test to see the PCM has +12 @ A2 with ignition on, engine off, that he has +12V constant feed on A22, (both of which referenced to Pins A31 and A32, which provide the ground to the PCM.) I'll back out now thx
I have it copied from somewhere. If you're talking about A4, it's the sensor negative (-) meaning the pcm is providing that (-) to the sensors. Presumably if the "ground" (actually the negative connecton @ pins a31 & a32) to the pcm is bad, that output will be as well, so I would test to see the PCM has +12 @ A2 with ignition on, engine off, that he has +12V constant feed on A22, (both of which referenced to Pins A31 and A32, which provide the ground to the PCM.) I'll back out now thx
Last edited by 97grand4.0; May 31, 2019 at 01:39 PM.
CF Veteran
Joined: Nov 2015
Posts: 2,863
Likes: 201
From: syracuse ny
Year: 1997 230,000 miles
Model: Grand Cherokee (ZJ)
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
A4 reports at 12.44 volts.......
In the forum I searched how to disconnect the connector as it was being a bit difficult. I have been known to break connectors so I was trying to be as gentle as possible. An old post by one of the guys has the picture and pinout from what looked to be from an fsm...
this thread, post 12 https://www.cherokeeforum.com/f2/no-...d-help-230900/
In the forum I searched how to disconnect the connector as it was being a bit difficult. I have been known to break connectors so I was trying to be as gentle as possible. An old post by one of the guys has the picture and pinout from what looked to be from an fsm...
this thread, post 12 https://www.cherokeeforum.com/f2/no-...d-help-230900/
Thread Starter
CF Veteran
Joined: Jan 2014
Posts: 1,102
Likes: 364
From: Eustis, Florida
Year: 1996
Model: Cherokee (XJ)
Engine: 4.0
CF Veteran
Joined: Dec 2015
Posts: 2,139
Likes: 93
From: Syracuse, NY
Year: 1996
Model: Cherokee (XJ)
Engine: 4.0L
CF Veteran
Joined: Dec 2015
Posts: 2,139
Likes: 93
From: Syracuse, NY
Year: 1996
Model: Cherokee (XJ)
Engine: 4.0L
It showed that the PCM is grounded because that cavity was providing ground.
With key on you should be able to find the PCM providing 5v at cavity A17 (on the PCM). This will help show that the PCM also has positive voltage being supplied.
If ground and positive are shown to be available at the PCM (what the above 2 tests are trying to show). Then I think the next move is to try a known-good PCM.
With key on you should be able to find the PCM providing 5v at cavity A17 (on the PCM). This will help show that the PCM also has positive voltage being supplied.
If ground and positive are shown to be available at the PCM (what the above 2 tests are trying to show). Then I think the next move is to try a known-good PCM.
CF Veteran
Joined: Jan 2017
Posts: 3,425
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From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
Does that mean it's time to take the PCM apart?
Did you try reseating the PCM connectors and/or doing the wiggle test? If you're about to replace the PCM I guess it doesn't make much difference if there's one broken connector or 96.
You guys are spending a lot of time on A connector, but did you look at B? Specifically, disconnecting Vehicle Speed and Oil Pressure Sensors?
Let's go back to this. Fuel Pump and/or ASD Relays engaged, albeit briefly.
Another good test (especially since it's free) is to see if more than one sensor has an issue. Disconnect ALL of them and see if PCM wakes up.
Did you try reseating the PCM connectors and/or doing the wiggle test? If you're about to replace the PCM I guess it doesn't make much difference if there's one broken connector or 96.
You guys are spending a lot of time on A connector, but did you look at B? Specifically, disconnecting Vehicle Speed and Oil Pressure Sensors?
no obd2 connection with TCM disconnected
no obd2 connection after reconnecting TCM
I noticed that after I reconnected the TCM and the battery, when turning the key to the on position I heard a click from the engine area. Turning the key off after obd2 connection failure and turning the key back to the on position did not recreate that click.
no obd2 connection after reconnecting TCM
I noticed that after I reconnected the TCM and the battery, when turning the key to the on position I heard a click from the engine area. Turning the key off after obd2 connection failure and turning the key back to the on position did not recreate that click.
Another good test (especially since it's free) is to see if more than one sensor has an issue. Disconnect ALL of them and see if PCM wakes up.
CF Veteran
Joined: Jan 2017
Posts: 3,425
Likes: 407
From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
And inspect as much of the wiring harness as you can, especially around heat and constant contact. It would seem a shorted wire would be just as likely (if not more) as a failed sensor.
Last edited by Dave51; Jun 1, 2019 at 10:16 AM.
CF Veteran
Joined: Jan 2017
Posts: 3,425
Likes: 407
From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
