Electrical CCRM / Inertia switch / something else?

Hello everyone,
I currently have a 2000 GT 4.8L that I just supercharged. Car has been idling and running fine before the supercharger, and including now (as of right now I'm datalogging, no full pulls, staying out of boost).
Today, my tuner came to make some adjustments and I started the car and began warming it up. It died on its own. I tried to start it but it continuously cranked and I no longer could hear my loud upgraded fuel pump kick on. I also noticed, dash ( - - - - - ) marks on my instrument cluster where my mileage would be. During this time as well, OBD2 port was in operable.

My car does not have factory anti security - the theft light does not engage (has never before nor does it now) so I believe the PATS syndrome is out of the equation.

I began checking all fuses/relays that I could access in the engine bay, and foot panel compartment.
Within the foot panel compartment, Fuse #2, #8, and #35 (fuse 2 and 8 per manual state Engine Controls, 35 PCM and a few other things not related to engine running - I'm away from the car and manual right now but I do remember PCM) - those fuses showed ZERO voltage on both supply and load side with key on/off.

Then, I decided to check the inertia switch in the trunk. It was not "activated", but I decided to unbolt it, and check for voltage. NONE.

I believe the CCRM gives voltage to the inertia switch? and controls a bunch of other functions yes? A post by @wmburns said no CCRM, no PCM on a post I found on another forum. If that's true it would make sense why fuse 35 aint seeing anything..

Anywho, I plugged the inertia switch back in and I heard a buzz! I went back into the car and noticed my mileage is now being show, and the car starts with ease.

Could this be a sign of a bad CCRM or Inertia switch?

Also, I took voltage readings as the car was running (when it started back up). Fuse 2, and 8 had voltage, yet 35 did not.

Any help is GREATLY appreciated!

wmburns said:

The ignition pilot duty circuit fuse is F2.34 (not F2.35). So telling me about fuse F2.35 doesn't help. Need to know about fuse F2.34.

As a reminder there are multiple parts to the CCRM. It's not just one relay but a series of relays under a single cover.

If looking for a WAG, your upgraded fuel pump is drawing enough power to pull down the system voltage enough to cause the CCRM to drop out. When you disconnected the fuel pump this allowed the CCRM to "latch up". Perhaps there's a weak ground somewhere that's not up to the task at hand.

Howto perform charging system voltage drop test

Howto perform charging system voltage drop test

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thank you for the response! A lot of the info I’ve dug up came from you and I’m glad to hear your expertise

F2.34 shows voltage. Unsure what results with F2.34 you would like me to address. (Key on/key off voltage measurements?)

I understand the CCRM is a series of relays, which sadly requires the change of the entire unit if one relay no longer works correct?

sorry, my knowledge is not as strong with electrical. I just tried to research as best I could before posting on here. But what’s a WAG?

wmburns said:

WAG=Wild Ass Guess

Most people service the CCRM as an assembly. However if you are good with a soldering iron it is possible to repair it yourself.

However I don't see proof that your CCRM is bad and that something external to the CCRM is actually causing the symptoms. Best to make sure that the CCRM has what it needs to function before replacing what maybe a good part. IE does it have POWER(s) and GROUND(s). Plus the "pull up" key on signal from fuse F2.34.

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okay I’ll try to gain access to the CCRM within the next few days and check what you’ve stated above and report back. I’m back at work for 24 hrs at a time, so hopefully I’ll have a nice day off to attempt to get at it again. Thank you

I have 11.6 at f2.34 when key is turned on. It’s quite low, but this could attest to me running so much key on tests with not starting the car in a while?
I have since, placed it on a charger. In a few minutes I decided to check for voltage and heard my fuel pump prime, and saw voltage at f2.2 and 2.8.
I turned the key a few more times and the voltage disappeared and pump no longer primed. I remember reading thru a few of your posts @wmburns and seen you wrote how critical battery voltage was. Idk what the next step would be. At this point, I’m thinking battery (highly due to the fact I have no idea how old the battery is, I bought the car in February 2019 - battery is VERY clean, zero corrosion but that still doesn’t tell me how old lol)
Or CCRM still?

The car is still on the charger and the charger says 43%. Once again, thank you for your help

edit: battery fully charged. As soon as I disconnect the charger my volt meter reads 12.9 and drops to about 12.7. My grounds are good, and I guess I could check for a drain - that would be later this afternoon if anything time permitting - but not knowing the age of the battery just might be it? I could also measure it as the car cranks too?

thanks for all the help so far burns

wmburns said:

Here's what I think. To know if 11.6 volts at fuse F2.34 is a problem you need to compare the voltage at the battery. IF the battery voltage is also 11.6 volts, then there is almost no voltage drop in the F2.34 circuit. If true, this is NOT your problem.

I also do not believe that having only 11.6 at fuse F2.34 is low enough to be the cause of the CCRM not latching up. To me it seems far more likely that there is a bad ground either to:

• The battery itself.
• the radiator core support
• The CCRM
• The PCM.

The fact that it wasn't working and then suddenly started to work also tells me it's a loose connection or ground.

But. Why are you making your life more difficult with such a weak battery? Why take the chance that your problem is being caused by something so basic as a weak battery or loose battery cable? Trouble shooting electrical is hard enough as it is. Don't make it even harder.

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The difference is battery 12.26 and f2.34 12.16. Pretty minimal? (EDIT: with key on)

I forgot about the radiator core ground. I’ll go ahead and check that. And might as well grab another battery. When I crank it it’ll drop to 10 ish volts
thanks for the help burns! I feel like we’re getting closer

So I went to Oreillys to load test the battery which case out good.
The guy working behind the counter said I could purchase the CCRM (since there was only one left in stock) and actually return it, if it didn’t work. Kinda hard to pass that up!

I switched out the CCRM and everything works great now. Fuel pump primes, cluster works with no dashes, OBD port communicates, car starts and runs once again.
@wmburns , thank you for your help and expertise. It was this, and multiple threads by you that also helped lead to the successful conclusion