No spark help! What did I forget to check?
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
So based on this read, What I think I understand is-
The key should react the same way as my friends GC (sorry to keep bringing it up but it fits the bill pretty well)
With the radio freq going to the key and back.
Also my key, being from a different PCM
Will need to be synched with this new PCM?
I am wondering why the light is solid and not flashing as previously described?
Here is a pic to confirm what I think looks like the SKIM.
(blurry camera sorry did the best I could)

The key should react the same way as my friends GC (sorry to keep bringing it up but it fits the bill pretty well)
With the radio freq going to the key and back.
Also my key, being from a different PCM
Will need to be synched with this new PCM?
I am wondering why the light is solid and not flashing as previously described?
Here is a pic to confirm what I think looks like the SKIM.
(blurry camera sorry did the best I could)

Let's not disconnect the SKIM wire harness connector at this time.
~~~~~~~~
As far as "I am wondering why the light is solid and not flashing as previously described?", here's what it said about a steady light on:
If the SKIS indicator lamp comes on and
stays on after the bulb test, it indicates that the
SKIM has detected a system malfunction and/or that
the SKIS has become inoperative.
~~~~~~~~
You asked: "Also my key, being from a different PCM
Will need to be synched with this new PCM?"
Key and SKIM are to be Reprogrammed together. If you read through that data I posted you'll see how they work together. DRB III tool task, by the dealer.
~~~~~~~~
I'll look for the new pic first thing in the morning.
Thread Starter
Seasoned Member
Joined: Dec 2010
Posts: 318
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Year: 2000
Model: Cherokee
Engine: 4.0
Well master mechanic came by today with his $10,000 Scan tool.
I am not getting cam sensor signal at all. Everything else is getting signal great.
New Napa cam sensor, and syncrhonizer.
Would the immobilizer cut cam signal?
Or do I have to yell at Napa
I am not getting cam sensor signal at all. Everything else is getting signal great.
New Napa cam sensor, and syncrhonizer.
Would the immobilizer cut cam signal?
Or do I have to yell at Napa
CF Veteran
Joined: Aug 2010
Posts: 1,168
Likes: 4
From: Williamsport, Pa
Year: 1997
Model: Cherokee
Engine: 4.0L
A transponder sensor will always be a plastic ring that fits around the key cylinder. It will be removeable if the top colume cover is removed and it will have very small gauge wires going to it, usually 4 to 5.
From the picture I do not see a transponder sensor/pickup. It may be possible that your Jeep didn't come with a transponder system so your original computer just flashed the light and then made it go out- probably programmed that way. The vehicle that you got the new PCM from probably had a transponder system and therefore needs to see the right "code" in order to start the engine. So if your Jeep never had the system in the first place you won't be able to program it.
If your key fob (the plastic end of your ignition key) is grey then your vehicle has an antitheft system. If your key fob is black it did not come equipted with one and you'll probably need to find another computer.
From the picture I do not see a transponder sensor/pickup. It may be possible that your Jeep didn't come with a transponder system so your original computer just flashed the light and then made it go out- probably programmed that way. The vehicle that you got the new PCM from probably had a transponder system and therefore needs to see the right "code" in order to start the engine. So if your Jeep never had the system in the first place you won't be able to program it.
If your key fob (the plastic end of your ignition key) is grey then your vehicle has an antitheft system. If your key fob is black it did not come equipted with one and you'll probably need to find another computer.
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
Cam/crank Sensor Diagram. Note that the 5 volt supply voltage to the Cam and Crank Sensors goes through splice S115.

Cam Sensor connector pin-out. To check for the 5 volt supply voltage at the Cam Sensor connector, turn the ignition switch to RUN (Don't Crank the engine), touch pin socket 3 with the meter positive probe and pin socket 2 with the negative probe - you should see 5 volts +/-. If you don't see 5 volts, place the negative probe to the engine structure. If you still don't see 5 volts, check the splice connections at splice S115.

Splice S115 components. As you cn see there is alot of sensors spliced at S115.

Slice S115 location. If you are not getting the 5 volt supply voltage at the Cam Sensor connector, you may want to unwrap the loom and tape at splice S115 and check the connections there. Note that all the sensor 5 volt supply wires at S115 are Organge. The Cam Sensor and PCM wires are 18 gauge and the rest are 20 gauge (slightly smaller than the 18 gauge wires).
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
You are seeing the immobilizer light on the instrument cluster come on during the bulb check, go off, then come on steady. This is supposed to indicate that the SKIM has detected a system malfunction and/or that the SKIS has become inoperative. In this case, the SKIM, and/or the Sentry Key may be at fault. I would suspect that POS SKIM.
If it has been confirmed that you do in fact have a SKIM, you might try this:
Disconnect the battery negative cable, detach the SKIM harness connector from the SKIM, reconnect the battery, try starting the engine.
I know you have a problem with the Cam Sensor signal which may complicate this whole issue. If the Cam Sensor issue can be resolved then you can focus on the SKIM.
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
What's a "synchronizer"?
Thread Starter
Seasoned Member
Joined: Dec 2010
Posts: 318
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Year: 2000
Model: Cherokee
Engine: 4.0
Well based on this I do have it, But I am going to double check anywho.
Looks like I know 100% I have SKIM. Thanks for the pictures!
I rechecked everything at key on it was as it should be.
5v signal, 5v power, nada at ground
Add to that it was 0.7ohm from cam side to PCM side of the signal wire.
Installed the new sensor, and nada!
Still nothing even tried switching between PCMs to see if it would make a difference.
What youre saying is a good idea, but also like you said figuring out what the hell is up with this cam sensor signal would be #1.
Not sure what it is called in Jeep terms haha
But the gear drive that drives the oil pump off the camshaft gear
5v signal, 5v power, nada at ground
Add to that it was 0.7ohm from cam side to PCM side of the signal wire.
If it has been confirmed that you do in fact have a SKIM, you might try this:
Disconnect the battery negative cable, detach the SKIM harness connector from the SKIM, reconnect the battery, try starting the engine.
I know you have a problem with the Cam Sensor signal which may complicate this whole issue. If the Cam Sensor issue can be resolved then you can focus on the SKIM.
Disconnect the battery negative cable, detach the SKIM harness connector from the SKIM, reconnect the battery, try starting the engine.
I know you have a problem with the Cam Sensor signal which may complicate this whole issue. If the Cam Sensor issue can be resolved then you can focus on the SKIM.
Still nothing even tried switching between PCMs to see if it would make a difference.
What youre saying is a good idea, but also like you said figuring out what the hell is up with this cam sensor signal would be #1.
Not sure what it is called in Jeep terms haha
But the gear drive that drives the oil pump off the camshaft gear
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
Well based on this I do have it, But I am going to double check anywho.
Looks like I know 100% I have SKIM. Thanks for the pictures!
I rechecked everything at key on it was as it should be.
5v signal, 5v power, nada at ground
Add to that it was 0.7ohm from cam side to PCM side of the signal wire.
Max resistance in these Jeep sensor wires to the PCM is supposed to be .5 Ohms, or less (per all the Diagnostics testing procedures).
Installed the new sensor, and nada!
What new sensor?
Still nothing even tried switching between PCMs to see if it would make a difference.
What youre saying is a good idea, but also like you said figuring out what the hell is up with this cam sensor signal would be #1.
What was I saying?
Not sure what it is called in Jeep terms haha
But the gear drive that drives the oil pump off the camshaft gear
Looks like I know 100% I have SKIM. Thanks for the pictures!
I rechecked everything at key on it was as it should be.
5v signal, 5v power, nada at ground
Add to that it was 0.7ohm from cam side to PCM side of the signal wire.
Max resistance in these Jeep sensor wires to the PCM is supposed to be .5 Ohms, or less (per all the Diagnostics testing procedures).
Installed the new sensor, and nada!
What new sensor?
Still nothing even tried switching between PCMs to see if it would make a difference.
What youre saying is a good idea, but also like you said figuring out what the hell is up with this cam sensor signal would be #1.
What was I saying?
Not sure what it is called in Jeep terms haha
But the gear drive that drives the oil pump off the camshaft gear
I can post the FSM procedures if you think you need to check your work.
Thread Starter
Seasoned Member
Joined: Dec 2010
Posts: 318
Likes: 0
Year: 2000
Model: Cherokee
Engine: 4.0
I asked the master tech yesterday (who got his start atchrystler) and he told me anythign under 2ohms is acceptable?
So then I would think I have aporblem with my signal wire somewhere?
The cam sensor is new, again haha
And I replaced the oilpump drive about 3 months ago, becaue the original one
(where it had the little metal tong for the cam sensor pickup)
Was actually loose and spinning freely from the oil pump drive shaft.
So this was actually messing up the reading for the cam sensor and causing misfires.
I put the new oil pump drive in with the sensor lined up properly with itself, and #1 pistion at TDC, on the comrpession stroke.
So then I would think I have aporblem with my signal wire somewhere?
The cam sensor is new, again haha
And I replaced the oilpump drive about 3 months ago, becaue the original one
(where it had the little metal tong for the cam sensor pickup)
Was actually loose and spinning freely from the oil pump drive shaft.
So this was actually messing up the reading for the cam sensor and causing misfires.
I put the new oil pump drive in with the sensor lined up properly with itself, and #1 pistion at TDC, on the comrpession stroke.
Thread Starter
Seasoned Member
Joined: Dec 2010
Posts: 318
Likes: 0
Year: 2000
Model: Cherokee
Engine: 4.0
Say it wasnt in synch as it should be,
I should still be reading some signal from the cam sensor shouldnt I?
So my next ideal is to trace the cam signal wire.
I think I am going to be lazy and see the signal it gets to the PCM.
I think I am looking for the signal wire to drop voltage correct?
Edit: oh sorry, Your idea that I should figure out about the cam sensor first
I should still be reading some signal from the cam sensor shouldnt I?
So my next ideal is to trace the cam signal wire.
I think I am going to be lazy and see the signal it gets to the PCM.
I think I am looking for the signal wire to drop voltage correct?
Edit: oh sorry, Your idea that I should figure out about the cam sensor first
Last edited by x91evo; Mar 22, 2013 at 06:16 PM.
Thread Starter
Seasoned Member
Joined: Dec 2010
Posts: 318
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Year: 2000
Model: Cherokee
Engine: 4.0
Checked everythign over again,
power wire to pcm 0.1ohm, 5.14V at key on
ground to pcm 0ohm, 0V key on
signal to pcm 0.1ohm, 5.12V at key on
those were the reading with the connector off the sensor, I did not backprobe it
Was the answer in front of my face the whole time?
Is the signal wire supposed to see 5V at key on?
Or is power shorting to signal?
power wire to pcm 0.1ohm, 5.14V at key on
ground to pcm 0ohm, 0V key on
signal to pcm 0.1ohm, 5.12V at key on
those were the reading with the connector off the sensor, I did not backprobe it
Was the answer in front of my face the whole time?
Is the signal wire supposed to see 5V at key on?
Or is power shorting to signal?
Last edited by x91evo; Mar 22, 2013 at 10:28 PM.
Thread Starter
Seasoned Member
Joined: Dec 2010
Posts: 318
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Year: 2000
Model: Cherokee
Engine: 4.0
Well after watching several youtube videos, I figured out that no the signal wire should not always be getting 5V.
It should be between 0-5V alternating while the signal is being given.
Time to take apart the harness and have some "fun"
edit :
Well I ohmed inbetween power and signal pins, and get infinite resistance (when C1 isnt plugged into PCM.)
I cant find a break in either wire?
So how the heck it the signal wire getting 5v?
It should be between 0-5V alternating while the signal is being given.
Time to take apart the harness and have some "fun"
edit :
Well I ohmed inbetween power and signal pins, and get infinite resistance (when C1 isnt plugged into PCM.)
I cant find a break in either wire?
So how the heck it the signal wire getting 5v?
Last edited by x91evo; Mar 23, 2013 at 12:25 AM.




