Wow - never seen this one...

DamageINC · September 17, 2008

2003 7.3, intermittent stall, starts right up afterwards.

Only code in PCM is a P0603. No chip, totally stock, 120k miles.

Did the cam sensor recall, and then upsold a bunch of maintnance (brakes, door ajar switch, so on..) Go to pull out of my bay to drive it, and boom - shuts off. Like someone turned the key off, no sputtering or anything, just died.

Noticed that the battery light would flicker in sync with some clicking from the fuse panel area. Turns out that the IDM relay is just hammering away when this happens.

Try another relay - problem persists. Noticed that I can get the clicking to happen during a simple key-on cycle, as long the key's been off for a couple minutes. Sometimes it clicks for around 2 seconds, other times it's just a fraction of a second.

With the PCM relay out, the problem won't happen because the IDM relay gets it's coil-side power from the PCM relay.

I check power at Fuse 22 to see if it's power from the PCM relay cuts in and out with in sync with the clicking - it stays on solid. Just for grins, I check for solid power at 86 on the IDM relay - it's good too.

I clamp my test light's ground side to terminal 86 on the IDM relay, and the probe-side of the test light to terminal 85. Sure enough - the light flickers in sync with the clicking IDM relay now. With a good power source to 86.

I'm gonna overlay that wire from the ground-side of the coil to the PCM, but I think that the problem's internal to be honest, just for whatever reason, the PCM's not holding a solid ground to the IDM relay's coil side.

Anyone here seen that before?

Dave

Bruce Amacker · September 17, 2008

Not on a PSD, but that's a common pattern failure on IH chassis. The IDM relay chatters when there is a lack of good power and ground to the PCM/IDM. Better double check your voltage drops at the PCM/IDM power and grounds.

Good Luck!

/forums/images/%%GRAEMLIN_URL%%/grin.gif

Tony302600 · September 18, 2008

Been there done that with the same concern, found pigtail for the IPR rubbing away the power feed to ground. Does the same concern. But i couldn't communicate. I also have gotten shocked (literally) by touching the drivers valve cover because the power feed for bank 1 injectors was rubbing on the passenger valve cover.

DamageINC · September 18, 2008

Really?? That's messed up.. I'd be interested to know how that problem created an intermittent ground for ckt 814 because the diagram shows NOTHING else on that circuit. Just a straight wire from the ground side of the coil in the relay, right to the PCM.

Dave

DamageINC · April 22, 2009

I can't believe I forgot to post what I found on this - it was a hell of a learning experience.

Every now and then you run into one of those scenarios where the solution defies all logic and shows no regard for any amount of training, experience, and know-how that you've acquired. This was certainly one of them for me.

Long story short, I absolutely triple checked every single power and grounds to the PCM and anything that could be related, load tested the complete circuits with a 4 AMP FOG LIGHT BULB just to make sure that everything was physically in good shape before I install a fresh new $900 PCM.

After all of this preparation and re-checking, I would have bet my left arm on the PCM fixing the concern. There was literally nothing else I could fathom to elimnate as a possible cause of this concern.

In goes the new PCM.

I made it about 3 feet out of the shop before the truck died and the clicking started up again. I couldn't believe it.

It was at this point to where I'd realized that any form of conventional thinking was not going to solve the problem, so I resorted to doing things that simply made no sense to a degree, and eventually found the problem that way. Even though all the power circuits were heavily load tseted, and should then realistically be in good shape (a Fog Lamp bulb draws WAY more current than any of the other circuits in question) I decided "What the hell" and started jumping B+ voltage to all the "known good" power sources at the CJB/Fuse box under the dash. Oddly enough, when I'd jump B+ to the power side of the coil for the IDM relay, the problem would go away. AGain, even though everything load tested fine.

I pulled the fuse box thinking that I maybe had an internal issue with the fuse panel, for some reason the coil side of the relay wasn't getting enough current THROUGH the CJB. But after disassembling it and checking everythign throughly, I came up empty handed again.

After some more head scratching, I wondered if maybe the fuse box itself was recieving good power, even though testing seemed to show that it was recieving more than enough juice. Besides - everything that ran through the CJB worked like a charm. Power windows, wipers, blower fan, radio, lights, EVERYTHING I could turn on I had turned on a simultaneously at one point just to make sure that it wasn't a power feed / low current supply issue.

It was.

That fuckng junction stud beneath the air filter box on the 7.3's that connects the B+ cable to the CJB was corroded to shit. There was virtually no cable left at all once I took the cover of. I was leveled, all the time I wasted on what should have been an extremely basic diagnosis. Like I said though, I had no reason to believe that there was a problem tere - everything worked fine, load tests came out flawless, there were NO OTHER CONCERNS except an intermittent stall followed by the clicking. For whatever reason, even though everything worked fine, the corrosion was enough to starve the PCM of the juice required to keep the IDM Relay coil driver closed.

Bruce was basically 100% correct, it was a lack of power to the PCM. Just, testing didn't show that there was a lack of power.

So that was the big ass kicker for me last year... don't think I'll ever forget that one.

BTW - I think it probably cost about $2 to fix properly.

Dave

mchan68 · April 22, 2009

Well, I'm glad I'm not alone. Read my thread about the cylinder #4 injector fiasco, and you'll know I sure took a good hooping on that one.

Bruce Amacker · April 22, 2009

load tested the complete circuits with a 4 AMP FOG LIGHT BULB just to make sure that everything was physically in good shape

May I offer some constructive criticism? This 4 amp fog light was not nearly enough draw to properly check the system. Two things you could have done better:

1. Use a higher amp draw load to test the system. I have not only a sealed beam (that only draws 2.2 amps, IIRC) but a blower motor that draws about 10 amps. I'm guessing you hooked up the fog lamp and judged the circuit "good" by the brightness of the lamp. Right? Posted Image

2. Using any load, if you had voltage dropped the circuit while the load was in place, I'm betting you would have found the fault very quickly. This means using the PCM (engine running) as a load, or your fog light. Hook a DVOM from B+ at the battery positive post to the PCM power input (pin 71 or 97 with a BOB), or backprobe the PCM power relay output terminal, or even ANY fuse in the fuse box would have shown your problem quickly. A: The circuit must be loaded while doing this test (circuit on, which means motor running). B: Voltage drop from B+ to the load should be less than .5v.

Even your small fog lamp probably would have shown VD out of range if properly tested. Example: Hook up fog lamp at either the PCM power in or PCM power relay. Check VD from B+ to the hot side of the fog light. I'd be willing to bet it would have shown high. The problem is you "trusted" your eyes to tell you the fog lamp was bright enough, and it might have been running on a 2v drop. BTDTGTTS.

In the future, hook up a BOB if you have one and run your voltage drops according to the book. If you don't have a BOB, you can probe the output of the power relays for your test location on the positive side quite easily. You'll have to backprobe the PCM connector (7.3 104 pin) or pierce (ugh!) the wire to get a test point.

Note- I'm pretty sure you can backprobe the 7.3 PCM but not the 6.0 PCM. With a 6.0 you've got to buy the $300 BOB adapter.

PS: Don't EVER hook power or ground to a BOB to jumper the circuit. Those 30 gauge wires won't handle ANY amperage!

Have a great day!

Posted Image

DamageINC · April 22, 2009

You're absolutely right, Bruce. I think I just kinda disregarded the potential for a power supply issue to the CJB because I'd assumed that running the truck with all the accessories on full-tilt would be plenty of load for the problem to become apparent if indeed it was that, considering that sometimes I could get the clicking to occur simply with a key-on cycle. And like I said, ALL of the accessories worked flawlessly regardless of how much was going on at the time.

This was like 6-7 months ago when this vehicle came in, looking back on it, I really wish I'd have checked the VD under load now... I like to think that I'm a pretty well versed with my electrical diagnosis but this one made a fool out of me, lol. It's good to get smoked every now and then though Posted Image

Dave

Fredsvt · April 23, 2009

I've seen similar with the IDM relay and fuel pump relay would click wildly while cranking (no start).

This was on a truck that had this no start issue and the customer put in 2 batteries and an alternator.

He could only start it by giving it a jump.

When I got it, I noticed the new parts, but the corroded battery terminals, I removed the terminals and inside them, they were so "white" that they made a very poor connection. I cleaned them up and wow! It starts right up.

The guy wasn't too happy, as his old batteries tested good and probably the alternator was good too.