Possible CCRM Issue

skimbap

Member
Jul 13, 2020
15
2
13
26
California
My 1995 Mustang V6 cranks but won't start.

What I've checked so far:
- All the fuses in the underhood fuse box are good
- Fuel pump doesn't prime. Used a fuel pressure test kit and there is no pressure at the Shrader valve when I put the key in the run position.
- No voltage going in or out of the inertia switch

I found this resource (https://sites.google.com/site/sn95mustangs/tech-info/94-95-ccrm) that says: "At the CCRM (Constant Control Relay Module – the black box mounted on the radiator overflow bracket): With the key turned to run, check Pin 12 and 24 for accessory power. If it’s there, the issue lies past the CCRM. If there’s no power: Check CCRM Pins 8 and 10 for constant 12 volts. Check CCRM Pin 13 for accessory 12 volts. Check CCRM Pin 15 for ground. If 8, 10, 13 and 15 are present (this requires the key to be on), but 12 and 24 are not showing 12 volts, that suggests a bad EEC relay inside the CCRM."

I did the following testing on the connector that connects to the CCRM on the radiator overflow bracket while it was disconnected from the actual CCRM:

- Used test light on pin 18 while attached to (+) on battery - test light did not turn on when car turned on or while cranking
- Used test light on pin 12 while attached to (-) on battery - test light did not turn on when car turned on or while cranking

I decided to just test all the pins while I was at it. Tested them all with test light attached to (+) and then to (-) on battery

At the following pins, the test lamp turned on while connected to (+) at the battery with the car off: 1, 2, 6, 7, 12, 13, 15, 24. No other pins caused the test light to turn on, even right after car turned on.

At the following pins, the test lamp turned on while connected to (-) at the battery with the car off: 3, 4, 8, 10, 11. Only one other pin turned the test light on when the car was turned on: 13

Pins 5, 14, 16, 17, 18, 21, 22, 23 never resulted in test light turning on.

Not sure what to do next or what the resolution would be. Any help would be appreciated! Also, not sure if HISSIN50 is still active on this forum, but the resource also says to refer to that user for questions.
 
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wmburns

SN Certified Technician
Aug 14, 2009
5,849
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Houston Texas
Is there power in/out of fuse I/P #18 with the key on? If not, suspect a problem in the ignition switch.

IF there's no power at CCRM pin #13, THEN the problem is not in the CCRM.

But you state there is pin #13 power. So we need to confirm a good ground at pin #15 (black with white stripe) before calling the CCRM.

Be sure to get the correct CCRM for your model year and engine. All CCRM's are not the same.



.
 

skimbap

Member
Jul 13, 2020
15
2
13
26
California
Is there power in/out of fuse I/P #18 with the key on? If not, suspect a problem in the ignition switch.

IF there's no power at CCRM pin #13, THEN the problem is not in the CCRM.

But you state there is pin #13 power. So we need to confirm a good ground at pin #15 (black with white stripe) before calling the CCRM.

Be sure to get the correct CCRM for your model year and engine. All CCRM's are not the same.



.
There is no power at pin 18 with the key on. Not sure what I/P means. I guess I’ll have to try replacing the ignition switch. I didn’t mention this in my original post because I didn’t think it would be relevant, but I am able to turn the ignition and crank even without the key. Would that be related to this?

And yes, there is power at #13. I also. confirmed that there is ground at pin #15.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,849
505
204
Houston Texas
I didn’t mention this in my original post because I didn’t think it would be relevant, but I am able to turn the ignition and crank even without the key. Would that be related to this?
Yes it could be. However in your case it may be a worn out lock cylinder AND a worn/bad ignition switch. Both can be changed by the DIY'er and do not require reprogramming PATS.

But why guess? Test! I/P fuse #18 is the pilot duty ignition circuit. Power in this fuse is what "causes" the CCRM to "latch up" and power everything else.

I/P = instrument panel = the fuse box under the dash.

However, with:
  • A good CCRM ground
  • power at CCRM pin #13
  • no power at CCRM pin #12 and #24
The only real conclusion is a bad CCRM.
 
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skimbap

Member
Jul 13, 2020
15
2
13
26
California
Gotcha! I tested pin 18 on the CCRM connector earlier, so ignore that. I tested I/P fuse #18 and it had power with the key on.

Thanks for helping me narrow down the issue. I've ordered a replacement CCRM that should be coming in this weekend, and we'll see if it fixes the no-start condition!
 

skimbap

Member
Jul 13, 2020
15
2
13
26
California
Yes it could be. However in your case it may be a worn out lock cylinder AND a worn/bad ignition switch. Both can be changed by the DIY'er and do not require reprogramming PATS.

But why guess? Test! I/P fuse #18 is the pilot duty ignition circuit. Power in this fuse is what "causes" the CCRM to "latch up" and power everything else.

I/P = instrument panel = the fuse box under the dash.

However, with:
  • A good CCRM ground
  • power at CCRM pin #13
  • no power at CCRM pin #12 and #24
The only real conclusion is a bad CCRM.
I replaced the CCRM (made sure it was the same part number) but it still won’t start. I still don’t hear the fuel pump priming, and I’m getting no fuel pressure (checked with gauge at the Schrader valve). Not sure where to go from here. I checked for power at the connector next to the fuel tank (for the fuel pump) with the key in the run position, and still not getting power there. What the heck is going on
 
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skimbap

Member
Jul 13, 2020
15
2
13
26
California
Update from my previous comment: I also replaced the ignition lock cylinder. I checked for power at the inertia fuel shutoff switch - no power there. Is this boiling down to an electrical issue, maybe somewhere in the wiring?

I also found this resource that says it might be the clutch safety switch, but I'm not sure about that
 

skimbap

Member
Jul 13, 2020
15
2
13
26
California
Got a mechanic to check this out. Turned out to be a faulty wire. It was under the trim/carpets on the drivers' side. Seems like someone did a bad job with some wiring on an aftermarket alarm system and messed up the wiring for the fuel pump.