1999 Mustang Gt 5 Speed Pcm Communication Problems

[Deepoo9]

Hello...Having troubles with my daughters 1999 Mustang Gt 5 speed convertible.

Engine cooling fan picks up as soon as you turn on ignition switch . Engine starts and stays running but has a flashing theft light, tach not working and runs super rich. Found two blown fuses while doing an ohm meter check of each one individually on the bench and replaced them...no change. Checked for codes with a scan tool and it could not connect to PCM, Tried another code reader and had the same problem. Was running fine before this happened.

Any help would be appreciated. Thanks!

 

[COramprat]

Count the theft light flashes. Should be in a set of two repeating flashes.

 

[Deepoo9]

Thanks Mod Dude for the reply!!

Eventually they flash a sequence of 1 then 6.

Also when I tried to move the car to put it on a trailer it would not start tonight. Until this evening it ran, but super rich, during the previous few days...engine cooling fan still comes on when key is turned to run, as well as the odometer is still all dashes.

At this point I am 99% sure the fuel pump is not running.....at least nothing on the gauge I plugged into the Schrader valve on the fuel rail when I cycle the key to start the prime sequence...I do here a slight hum from the CCRM for a few seconds. In addition also re-checked all the fuses with my ohm meter and they are still good. I have not checked the ground under the battery that I read about in other posts, but intend to.

For what it is worth I have been told by a fellow shad tree mechanic the CCRM may be the issue because the symptoms have not been constant.

Any ideas??? Thanks in advance for any additional info.

 

[wmburns]

Engine cooling fan picks up as soon as you turn on ignition switch . Engine starts and stays running but has a flashing theft light, tach not working and runs super rich. !

Running super rich and the cooling fan running at initial key on are symptoms usually associated with a bad PCM.

NOTE, a bad or no power to the PCM will CAUSE a PATS failure.

 

[Deepoo9]

First of all thanks for replying wmburns !! I see your posts on a lot of the tech problems other members submitted ..And I appreciate you taking time to offer some direction on my concern.

I was wondering where it would be best to probe for power to perform this check?

I also want to share that the fan and PATS/Communication issues came after I unplugged the fuel pump connector under the rear bumper cover in an attempt to see if I could not hear the fuel pump running the prime cycle. Before the "unplugging" the car had ran fine to the parts store for oil change supplies. But when I started the car to drive home it idled fine but would not take throttle. I limped home and proceeded to start the checks for power to the pump. I replaced the 2 blown 20 amp fuses I discovered, but no changes...still had the com and PATS issues.

I do have a spare CCRM and Fuel pump control module I removed from a 2000 gt my neighbor crashed with 16,000 miles on it .

Please let me know....Thanks

 

[wmburns]

It would help the trouble shooting if you posted WHICH fuses were blown.

Also did you confirm that the fuses didn't just blow again or if there were any others?

As for probing, use a volt-Ohm meter (VOM) to test for key on voltage the Central Junction Box (CJB=F2) fuse F2.2 and F2.8.

IF no power suspect:

• blown fuse
• bad CCRM
• bad ignition switch

If there is power suspect:

• bad PCM
• Still could be a bad CCRM

Also test for key on voltage at the trunk mounted IFS switch. There should be voltage at the IFS switch the entire time that the ky is on.

Where to look next depends upon the test results.

 

[Deepoo9]

I am sorry, you are correct, I should have posted them as you stated....Sorry about that. They where the #2 20 amp engine control fuse in the cars interior fuse panel and the PCM power 20 amp fuse under the hood.

I pulled 100% of all the fuses in both panels out tonight, one at a time, and carefully checked each one with my ohm meter on the bench and they were all still fine.

I pulled # 2 and 8 fuses under the dash and probed the sockets for power. They were both ok...12V. Then I put the fuses back in place and checked for 12 volts and there was power across both of them.

Finally I pulled the plug off the IFS and there was power on one wire when the key was on. I realized I probably should have checked for continuity across the switch once I got back in the house. But being I am in Seattle it is of course raining cats and dogs tonight so I don't want to go back out and check it now. The car is over in my outbuilding and I have just dried off from my trip over earlier this evening. I can do that tomorrow if need be.

I do have the CCRM I pulled from my neighbors crashed Gt located and on the bench in the shop if I need to try that.

In closing I appreciate you taking time to help me out!!!......Thanks so much....Deepoo9

 

[wmburns]

Let's loop back around and go through the current symptoms.

Does the motor run at all?

Does the cluster display all dashes ("-------")?

Does the fuel pump run at initial key on?

Are you able to talk to the PCM with a scan tool?

Does the cooling fan come on when the key is first turned to on? Are you certain that the CORRECT CCRM has been used? Note, there are differences in the model years and engine (V6/V8).

Honestly based upon the reported symptoms that IF the motor runs pig rich the odds favor a bad PCM.

 

[Deepoo9]

Ok....Does the motor run at all?....Yes it has, not 100% of the time.... very rich when it does...sounds like my drag car. I just checked it now and today it did not even try to fire.

Does the cluster display all dashes ("-------")?....Yes... the odometer still reads all dashes.

Does the fuel pump run at initial key on?. Honestly I can not hear it today, but it is in my house garage and the fan picking up makes so much noise I can't tell. Would it hurt to disconnect the fan at this point to recheck??

Are you able to talk to the PCM with a scan tool?...It seems to connect to check for codes ( shows none found which seems odd) , but not real time sensor data.....at least not any data with key on and not running. This is using a Diablo programmer. I have a Ford Factory scantool but have not tried it on this car as of now...it has the locksmith software I used it to resolve a PATS issue I encured after changing dash clusters on one of my other Mustangs.

Does the cooling fan come on when the key is first turned to on? ...Yes.

Are you certain that the CORRECT CCRM has been used?... The CCRM in the car is still the OEM supplied unit with 155K on it.
Note, there are differences in the model years and engine (V6/V8).

Once again thanks for your help..!!

 

[wmburns]

A couple of points.......

For the motor to even run, the fuel pump HAS to be running.

The fact that any ODB2 tool and the PCM can communicate means that the PCM is alive at some level.

The cluster displaying all dashes usually associated with:

• no power to the PCM. Clearly not the case because the PCM will communicated
• bad CCRM. the PCM is powered and the fuel pump is running. So will rule this out as well
• lost programming between PCM and cluster. Based on your last post, IMO this a REAL possibility.

The fan turning on at initial key usually means:

• bad CCRM. Ruled out based on other symptoms
• bad PCM. Not as likely as the PCM is talking.
• Incomplete PCM programming. IMO this is a REAL possibility as a hand held programmer was used on the PCM.

My vote is that somehow the PCM programming has become corrupt or the PCM is just plain bad.

 

[Deepoo9]

Thank you Sir...Before I responded I did actually take the time to question my daughter about using a programmer and found out that nearly two years ago she and her boyfriend took one of my old programmers ( a Ganatelli/Diablo) that was unlocked and reprogrammed this car.....for some reason. This was news to me. With that said, I got the programmer they used back from them and I assume the original files are still stored in that unit. Is it possible it could be used to restore the PCM or are the corrupted items more likely parameters other than the ones transferred out to be stored in the tool ???

If not possible, what would be the least painful way to restore my original PCM and/or the com with the cluster...if that is even possible?? I also have several 2001 Bullitt PCM's on had because I purchased several engine trans combos from 01 Bullitts with low miles thinking I would swap them into a couple of GT coupes at one time...Still have 3 of them and the PCM's and harnesses on hand

Now that you have helped me understand the potential root of the problem, I have an additional question about the fact it runs one day ( though super rich ) and will crank and not fire at all another day. Is there a business case to substitute the CCRM from the 13K wrecked Gt I salvaged from my neighbors totaled 2000 GT 5 speed car or would that be a wasted effort. I guess I am wondering if there may be an intermittent issue with the power to the PCM and/or the pump.

Thanks again... Deepoo9

 

[wmburns]

Let me help you answer your own questions.

IF this were an intermittent PCM power issue, how could this be ruled in/out? One quick way I can think of is to monitor the PCM with an ODB2 scanner. IF the PCM is loosing power, this will show up on the ODB2 scanner. If the ODB2 scanner is able to communicate with the PCM the entire time, IMO a base power problem to the PCM is not likely the cause of the problem.

Regarding a intermittent power problem to the fuel pump, If true, this could be ruled in/out by listening for the fuel pump to run at initial key on. Also, how would a fuel pump power problem CAUSE the motor to run pig rich? Regardless this can be ruled in/out by MEASURING the fuel pressure.

Regarding swapping other CCRM's. Note that there are differences between the model years and engines. Recommend confirming that any CCRM swap be checked by matching the part numbers. Otherwise you could be trading one problem for another.

Regarding swapping PCM, EXPECT problems if swapping a PCM from a different model. ESPECIALLY if going from a 1999-2000 MY to a 2001+. Also remember to match the transmission type (automatic vs manual) as well as the motor type (V6, V8 ect).

Does this PCM have an "add on" chip? If so, I have seen several case where dirty pins have caused strange problems.

At the risk of sounding rude, it seems to me that you are reverting to trouble shooting via "parts swapping". While parts swapping can sometimes be effective, random or shotgun style on a complex problem seldom is. Test more. Swap less. Think before doing any repair.

As to way this problem could come and go, look up Stoichiometric mixture (or flammability range). It possible that there's soooooo much fuel that combustion is not possible. Could be other things. Can't tell you for certain unless you can give me a bunch more information. I suspect that if you knew this, it might also solve the problem.

I would certainly attempt to restore the PCM before replacing. This could also help narrow down if the PCM is bad. IE if the programmer isn't able to re-program.

Since you didn't know about the programmer, it might also be wise to rule out some other changes. Say for example larger fuel injectors or a different MAF.

 

[Deepoo9]

Thanks for your reply..Trust me I don't view you as rude.

Copied your note and put replies in red.

IF this were an intermittent PCM power issue, how could this be ruled in/out? One quick way I can think of is to monitor the PCM with an ODB2 scanner. IF the PCM is loosing power, this will show up on the ODB2 scanner. If the ODB2 scanner is able to communicate with the PCM the entire time, IMO a base power problem to the PCM is not likely the cause of the problem. Is it fair to assume there is power there, at least sometimes, as the car does run from time to time??

Regarding a intermittent power problem to the fuel pump, If true, this could be ruled in/out by listening for the fuel pump to run at initial key on. Also, how would a fuel pump power problem CAUSE the motor to run pig rich? Regardless this can be ruled in/out by MEASURING the fuel pressure.I put a Pressure gauge on the valve to help determine if the pump is or is not running each time I turn on the key and try to start the car...When it runs there is fuel pressure and when it does not there is no pressure. I am not sure if the pump is funky or the CCRM is flakey

Regarding swapping other CCRM's. Note that there are differences between the model years and engines. Recommend confirming that any CCRM swap be checked by matching the part numbers. Otherwise you could be trading one problem for another.My spare CCRM is the same identical number as the one in the car.

Regarding swapping PCM, EXPECT problems if swapping a PCM from a different model. ESPECIALLY if going from a 1999-2000 MY to a 2001+. Also remember to match the transmission type (automatic vs manual) as well as the motor type (V6, V8 ect).

Does this PCM have an "add on" chip? If so, I have seen several case where dirty pins have caused strange problems. No add on chip of any sort.

At the risk of sounding rude, it seems to me that you are reverting to trouble shooting via "parts swapping". While parts swapping can sometimes be effective, random or shotgun style on a complex problem seldom is. Test more. Swap less. Think before doing any repair. No offense taken. I should share I have been a CNC Machine Tool Maintence tech for Boeing for 39 years. I am the lead of a group that builds custom CNC machines from scratch or modifies existing equipment for BCAG requirements, as they are so specialized no off the shelf equipment exists. So I fully understand the effect of shotgun repairs.

As to way this problem could come and go, look up Stoichiometric mixture (or flammability range). It possible that there's soooooo much fuel that combustion is not possible. Could be other things. Can't tell you for certain unless you can give me a bunch more information. I suspect that if you knew this, it might also solve the problem. I do understand Stoichiometric ratios..I actually have a lot of expierence with ECU controlled FI....But only with GM applications. Both my NHRA Stock class and my Super Stock class drag cars are injected 1999 Firebird Formulas. And sadly, even though I purchased factory shop manuals for each of my 5 Mustangs when I purchased them new,.....they have been so reliable I have not hardly opened them.

I would certainly attempt to restore the PCM before replacing. This could also help narrow down if the PCM is bad. IE if the programmer isn't able to re-program. As of today when I look for codes with the handheld tuner they used 2 years ago it says none are found. When I try to transfer the original factory program back it says there is no communication and as I stated before it shows no data for any of the monitored functions with key on engine off.

Since you didn't know about the programmer, it might also be wise to rule out some other changes. Say for example larger fuel injectors or a different MAF. Injectors are Yellow top Ford Racing and have been in the car since 100K ...MAF is untouched....not even CAI. Very original car except for ******* boyfriends endeavor using programmer 2 years ago ..unknown to me until now.

I will try to run fuel pump with external power supply tonight or tomorrow. It has a meter to allow me to see amp draw..that should either condemn the pump or validate it is still good.

Please let me know what is the best way to restore the PCM should I need to ...Dealer.???..One of the local Mustang tuners??? Other sources???

Thanks as always ...Deepoo9

 

[Deepoo9]

Put together a connector for the pump harness with a plug I got from the salvage yard and made the checks with my external power supply. Fuel pump ran fine. Next I disconnected battery and changed the CCRM .... the car started right up and ran fine. I took it for a ride around the block and everything seemed to work OK. Let it gat warm and fans came on ....AC works. I'll drive it for a couple of days before I give it back to my daughter.

Thanks wmburns for all your help on this problem!!

 

[herbs]

This is just an FYI for Mustang owners.

I was having problems for several weeks in 2018-19 with my 1999 Ford Mustang GT (V-8). Would crank but only start when it felt like it, would sometimes stall in traffic, would only run for a few seconds after starting, etc. Finally would not start at all.
Local Ford dealer thought it was a PATS (Passive Anti-Theft System) problem. Replacing the instrument cluster and
PATS transceiver did not help. Finally, they replaced the CCRM (Part #12B577 AA).
Problem solved.
Note: on a 99 Mustang, the CCRM is located near the top of the right front fender well. Must remove
the wheel and fender liner to access. Also, the only mention of the CCRM I could find in my Official 1999
Ford Mustang Shop Manual was in the Climate Control section (the CCRM has a relay for the A/C) but not a
word about it in the Fuel System section even though it has a relay that feeds the fuel pump.

 

[wmburns]

Note to anyone else reading this post. I generally try to discourage anyone to change expense parts such as a CCRM on a guess. On the 1999-2004 Model year it's possible to know with a fair degree of confidence if the CCRM is (or isn't working) by testing fuse F2.31, F2.2, F2.8, and the trunk mounted IFS cut off switch for key on power.

Best to use a test light that will "load" the circuit. Use a known good good ground.

IF there's confirmed key on power at fuse F2.2, F2.8 and the trunk mounted IFS switch, then the CCRM is working.

IF there's no power at fuse F2.31, then the problem is in the ignition switch.

OBTW, my Ford 1999 Ford wiring diagrams does show the CCRM on cell 024-008 Electronic Engine Controls

1999-2004 MY fuse panel schedule:
https://www.allfordmustangs.com/for...r-swap-wont-fire-please-help.html#post2669271

 

[SMOKEDYA]

Going to bring this back from the dead. 2002 GT cranks wont start, dash reads all dashes,no fuel pump no fans come on theft light flashes rapidly for a few minutes then gives a 16 code. Neighbor tried his scanner but the OBD II port is not communicating with the ECM it said. Power at the inertia switch, checked the CCRM power there as well. Previous owner installed new CCRM,key,key antenna,fuel pump