Electrical Relay Question

Clinton King · Aug 5, 2016

can anyone tell me what the relay on the right side of console by the radio is for? Also there are relays in a relay box on back side of fuse panel under dash that I can not find out what they are for either. It doesn't show them in owners manual. Thanks

Clinton King · Aug 7, 2016

anyone?

wmburns · Aug 11, 2016

OK, I give up! What model year Mustang are we dealing with?

There is the GEM module behind the dash.

It might also help if you took more time with your post. How about a full thread on what the base problem is and the recent work done?

squeak93 · Aug 11, 2016

Or snap a pic and draw an arrow for us.

Clinton King · Aug 11, 2016

2002 gt. Car won't start, theft light has blink code 16 instrument cluster has dashes in odometer, electric fan runs all the time when key is on and scan tool will not communicate. checked powers and grounds at ccrm, and pcm, and have everything and fuses all good. wires at pcm will also light a test light nice and bright so I don't have any corroded wires. also ohmed out data bus wires from pcm to obd connector and pcm to abs module and they are good. I have no power to coils. I'm thinking the pcm is bad. The relay I am referring to is on the right had side of the radio bracket under dash. (flasher is on left side in same location this on is on pass side instead of drivers side. The other relays I am referring to are directly behind the fuse panel under dash. I thought maybe one of these relays might have something to do with it but can't find out what any of them are for. Also does anyone know where the pats module is located? I wanted to chek data bus there also but I don't know where it is. Everything I could find kept saying it was in drivers side kick panel but I believe that is the gem module and there are know data bus wires there. If you still need a pic of relays I can get some when I get a chance. Thanks

Clinton King · Aug 11, 2016

First pic is dash panel I'm talking about and 2nd pic is relay behind that panel and 3rd pic are the relays on back side of fuse block under dash

wmburns · Aug 12, 2016

Clinton King said:
I have no power to coils. I'm thinking the pcm is bad.

IMO you are looking for your problem in the wrong area. It's not the GEM as the GEM will not prevent the motor from starting.

The PATS symptoms are being CAUSED by the PCM's lack of power. Remember that PATS requires a two way communication between the cluster and PCM.

A bad PCM will not CAUSE a no power condition to the coils.

This is far more BASIC. As in the PCM isn't getting any power. The clues are:

All dashes on the cluster
the cooling fan running all the time (fail safe cooling).
The PCM won't talk to a scan tool.
This is the most important detail. NO power to the coils.

Tell us about any recent work done to the car. How did you test the fuses? HOW did you check the grounds to the CCRM? Did you test using KNOWN good grounds?

Check for a large black wire with a white stripe that goes around the battery. It connects to a larger round single pin connector and is often disconnected during battery work. This is the CCRM/PCM ground.

Confirm there is "always on" power in and out of all fuses in the battery junction box (BJB=F1). If not STOP and find out why.

Perform all of the following tests and post the results. This will focus additional testing. Test for key on +12 volts at fuse F2.34, F2.2, and F2.8.

If no power in fuse F2.34, look for a possible bad ignition switch.

OBTW, the car will never start unless there's is at least power in fuse F2.34, F2.2, and F2.8. Not to mention, power to the Coil on plugs.

OBTW, IF all fuses are good, AND power to F2.34, AND no power to F2.2, AND the CCRM grounds are good, then the odds favor a bad CCRM.

Note, all tests for power should be done using known good grounds.

99-04 Fuse panel schedule:
http://www.allfordmustangs.com/foru...r-swap-wont-fire-please-help.html#post2669271

Clinton King · Aug 12, 2016

I agree it's not the gem module. I'm trying to find pats module and everything I found said it was in drivers kick panel which appears to me to be a gem module. I checked fuses with a meter. I don't have pin outs in front of me right now so I can't tell you specific pin#'s but with cram plugged in I had all powers and power going out to play and ground to battery was good (less than 10 ohms) don't remember exactly what it was. I also had all of the powers and grounds to the pcm (again I don't have pin out in front of me). So I just wanted to see what these relays were for in case they may be related to this but I can't seem to find any info on what they are for. Grounds from pcm to battery was .5 ohms (I do Remember that. As far as anything else goes I bought the car this way so I have no idea what has been done. I know it was in a wreck. I already checked inertia switch and someone before me had been probing around on wires to inertia switch and fuel pump which makes me wonder if they didn't fry something in pcm. I did open it up but didn't see anything but I've worked on semi's for 22 years and have found that you don't always see burned places. I sent pcm out to be checked so hopefully I will find out soon if it needed repair or not.

wmburns · Aug 14, 2016

Clinton King said:
if they didn't fry something in pcm.

Warning. Tough love follows.

"The force is weak on this one. Hope lost it is" <Yoda>

A bad PCM can not CAUSE a no power condition to the ignition coils. There is nothing in the PCM that can control key on POWER to the ignition coils. The PCM could be total smoking melted (even missing) printed circuit board and in an otherwise working car, there would still be +12 volts of key on power to each ignition coil.

I gave a series of easy to perform tests with tons of detail that with the results can quickly narrow down WHERE to look closer. I'm going to drop off of this thread as my input isn't helping.

Note, the analysis is based upon the reported symptoms. If any of the reported symptoms are wrong/incorrect, then the analysis will be incorrect as well. Your PCM may be bad or fried. But with a HUGE symptom such as no power to the coils, it's way too early to be thinking about a bad PCM as the reason WHY your car won't start.

If you are interested in getting a full set of wiring diagrams and service manual for your car I maybe able to help. PM if interested. The wiring diagrams will show how power flows in the Mustang.

Good luck.

90sickfox · Aug 14, 2016

How's the engine block ground ?

Clinton King · Aug 14, 2016

90sickfox said:
How's the engine block ground ?

From battery to block is 1.6 ohms and it's good and tight

Clinton King · Sep 5, 2016

wmburns said:
Warning. Tough love follows.

"The force is weak on this one. Hope lost it is" <Yoda>

Clinton King · Sep 5, 2016

So just to update my phone WAS bad and finally was able to get new one and installed it. What do you know now the fan isn't running all the time, my odometer reads mileage instead of dashes, I HAVE POWER To MY COILS, and my scan tool now communicates! Now I just need to get my keys programmed. So to mister "Yoda" I guess you need to retrain because " the force is weak with you" and I'll leave you with this thought.

wmburns · Sep 5, 2016

Thank-you for the update. However, I don't believe that you are telling the whole story. Somehow during all the work other repairs were made OR the stated symptom of "no power to the coils" was incorrect.

How do I know?

Because the SAME power feed from the CCRM that powers the ignition coils ALSO powers the PCM. The single wire goes to a splice and then branches to the engine VPWR ignition coils and then onto the PCM. This is per the Ford Factory wiring diagrams.

Go back and carefully read my original post. It was clearly stated that the PCM could indeed be bad. However given the symptoms as reported by YOU, it would be impossible for the PCM to actually be powered up IF there were no power to the ignition coils.

As a home mechanic myself I'm aware of how expensive a part a PCM is. I personally would hate to buy an expensive part only to find it was something else. If this were my car, the first set of trouble shooting completed would have been to positively find out why there was no power to the coils. Then re-tested PCM access.

I'm glad that it's fixed but I still stand by my post.

Clinton King · Sep 5, 2016

I am not a liar and I told everything that was going on. I'm on a limited budget and I don't like to replace things that aren't bad either that's why I posted on here and why it took me so long to get the part. What you say may be true but all I know is there was no power there before with old pcm and their is now. The ccrm also controls the fan and it ran all the time, so obviously all these components work together. Whether I'm right or wrong you don't need to basically call someone an idiot because apparently there is something that you must not be aware of as all of the symptoms I mentioned are now gone and I have not done anything other than what I have said I did. I thank you for all of the information but maybe in the future you can help people without saying they're dumb.

wmburns · Sep 5, 2016

At this risk of starting a thread war, did you perform any of the tests given in #7 before buying the new PCM?

Did you get any benefit from the information provided?

Did anyone else give you any useful information?

Clinton King · Sep 5, 2016

Yes I had already checked all those before starting thread! I had already looked at a thread similar that had all these checks just like I had already said. I just wanted to know what some relays were for which I still don't know.

wmburns · Sep 6, 2016

Reminder. We out here in Internet land know anything about your car beyond what is posted in your thread.

Recap. You performed some tests but failed to include the detailed results in the reply. This denied those of us trying to help you the information needed to formulate a meaningful/helpful reply. Your reply indicated that you were still focused on the PATS module as being a possible problem source. This in spite of the detailed information given to the contrary. Further your reply indicated that the action to be taken was exactly contrary to the advice given.

So from where I'm setting, my time was given to offer the best advice that I could based upon the information given. Requests for additional information were ignored (or not answered in an understandable way) and instead efforts were focused in areas advised against.

It was only then that satire was used to get your attention.

At the risk of beating a dead horse. There are (5) separate relays inside the CCRM. 1-PCM+ignition, 2-fuel pump power, 3-high speed fan, 4-low speed fan, 5-AC compressor coil. Relays 2-5 are controlled by the PCM. #1 is controlled by the ignition switch. So it's not really a surprise that the cooling fans started working correctly once the PCM started working.

You didn't answer the question regarding if you received any benefit from the information provided?

If you still believe that you are correct, then you wouldn't mind:

confirming key on power to the COP. Test between COP and a known good ground. Do not test across the COP itself.
disconnecting the battery negative
disconnecting the PCM electrical connector
re-attaching the battery negative.
testing for key on power to the coil on plugs? Again, use a known good ground.

If your analysis is correct then removing the PCM should also kill the power to COP's.

If it turns out that I'm wrong then as gesture of gratitude I'll send you a full set of Ford wiring diagrams and service manual. Seems like a very solid offer to me. Once you have these manuals then you will have all of the service information about your car at your finger tips. Best of all, you won't have to ask someone on the Internet what a certain relay is for.

EDIT: added details about how to test for power at the coil.

Clinton King · Sep 6, 2016

To answer your question no I found no useful info on this thread! I did however find useful information on this forum before asking this question in which you were the one giving the info on that thread. The info given was the same as you posted here and if this statement from you is true http://www.stangnet.com/mustang-forums/forums/SN95-46L-Mustang/ about where the easiest place to check for power is then yes I DO NOT have power to the coils with pcm unplugged! You gave great info but your satire was neither helpful nor got my attention in fact it just pissed me off and is why I have posted anything until now when I had new one in, and is why I am likely not to post on this site again! As far as the pats system I simply asked where it was located so I could check the data link wires from there to the pcm. I appreciate anyone willing to help others on these forums but no one wants to have your "satire" just because of a lack of understanding on one person or another's part. I thought I had made clear that I had done all the checks you stated with no problem found and wanted to rule out these relays in dash before sending out the pcm. I sent out pcm and they said the processor was bad and not repairable. I ordered a new one and all problems I had are no longer present. Now just got to come up with another 150 bucks to get keys programmed.

Clinton King · Sep 6, 2016

"Measure the key on voltage at the ignition COP circuit. Easiest place is the RED wire to the radio interference capacitors. Post." Sorry I don't know what happened with that link but here is the quote from that thread

Electrical Relay Question

Clinton King

Member

Clinton King

Member

wmburns

squeak93

Clinton King

Member

Clinton King

Member

Attachments

wmburns

Clinton King

Member

wmburns

90sickfox

Wasn't a pretty sight...and I've got big hands

Clinton King

Member

Clinton King

Member

Clinton King

Member

Attachments

wmburns

Clinton King

Member

wmburns

Clinton King

Member

wmburns

Clinton King

Member

Clinton King

Member

Similar threads

Electrical Relay Question

Member

Member

Member

Member

Attachments

Member

Wasn't a pretty sight...and I've got big hands

Member

Member

Member

Attachments

Member

Member

Member

Member

Similar threads

Privacy & Transparency

Privacy & Transparency