Hey all, I have an 88 F150 with a very peculiar problem. The truck will start and run fine, but it will randomly die after a few mins of running. After it dies, if you turn the key all the way back to the off position and go to restart it, the truck fires right back up. I flashed the codes, and code 18, which is "IDM CIRCUIT FAILURE OR SPOUT CIRCUIT GROUNDED," came up. I replaced both the ignition control module and the Hall effect sensor in the distributor. Base timing is set at 10 BTDC as per the factory. The wiring between all components ohms out fine, and is not open or shorted. I'm thinking this is a faulty PCM. Has anyone else had this issue? I bought a PCM off of eBay, just haven't had a chance to put it in yet. Figured I'd come on here to see if anyone else has had a similar issue. I really want to get this truck going again! It is my beast! Thanks in advance.

 

ive never heard of that, you said IDM in your post did you mean ICM?

 

That's a negatron sir, I thought it was a typo at first but it actually does stand for "ignition diagnostic monitor"

 

IDM (Ignition Diagnostic Monitor) is a signal derived from the ICM to coil to tell the computer the coil is firing.

It's the 22k ohm resistor on the far right side of the diagram below:

 

Rla2005, do you mean the 22kohm resistor is the issue? If that were the case, then if I were to take my ohmmeter and take a measurement, and if it was out of range, I have found the problem? Off the top of your head do you know where this resistor is located on an 88 f150? And thank you for the reply, this problem has been driving me nuts.

 

Some good IDM/Code 18 troubleshooting info in this thread: Seriously... Has Anyone ever dealt with a DTC Code 18.. Spout Ground? ICM issues - Ford Bronco Forum

This post describes where the ICM resistor is located: Ford Bronco Forum - View Single Post - Code 212 help needed

 

I believe the ignition coil failing or losing power can also trigger code 18

 

Rla2005, thank you for the info. I was able to get a chance to look into the truck some more tonight. Everything checked out good apart from one thing-according to the first link you sent, with an ohmmeter between the SPOUT terminal on the ICM harness connector and pin #36 of the ECM, the reading should read above 10K Ohms. When I took this reading I got 0 ohms. This is where my confusion comes in, judging by the wiring schematic, shouldn't the reading between these two points be 0 ohms? I checked for continuity to ground at pin #36 of the ECM and the spout terminal on the ICM harness connector, and neither have continuity to ground. So, if you or anyone else could shed some light on that, that would be great.

 

I believe they neglected to also state "Remove SPOUT".