Hope I am not overloading everyone with questions but I need to get this truck straightened out.

California Emissions Truck so it has the module not the solenoid.

Should the GPCM get hot to the touch?

I wanted to test the signal from the PCM to the GPCM. With everything hooked up and my meter hooked to the #8 lead on the Green connector, I disconnected the EOT and then with KOEO tested the voltage.

It read about 1.1 volts but never jumped up to the 11+ volts the manual said I should get after 2 minutes. If anything it seems as though the voltage was going down.

When I went to double check my connection I noticed the GPCM was very warm, almost hot to the touch. This is a new GPCM (second one I have tried) so I need to know if this normal.

Thanks.

 

Hot to the touch doesn't sound good, but I can't confirm anything for you. The kids sold their Excursion, so I have no reference to test for comparison. Hopefully someone who reads this has a GPCM and can check for you.

 

I guess I'm going to have to check the continuity in every wire for the GPCM and the Wastegate Solenoid.
These are the two codes (P0670, P1690) that I have been getting since I bought the truck.
Ugh! I had hope there was a common denominator to this problem that someone might have run across but so far nobody has volunteered one.

 

2000 excursion, key on 2 minutes, module got warm (90 degrees ish F.) defiantly not uncomfortable to keep my hand on it for 2 minutes.

 

Thanks.
I have another questions concerning diagnostic procedure.

Following a step by step .pdf file but I do not understand the following:
I was fine on QB7 and QB8 but this one has me confused.

Can I run this test without a breakout box?

I have the GPCM disconnected and the PCM unplugged as required in QB7. I have a test prob (stripped ends of appropriate sized wire so as not to damage connector) in the 101 pin on the harness.

My test results produced no continuity at all from the 101 pin to battery ground post.
However, I do not understand this statement and how it applies to this test. (Typical voltage should be 12 V.)

Here's the step in the manual:
QB9 CHECK FOR SHORT TO GROUND IN CONTROL CIRCUIT
Key off.
Connect PCM to breakout box; leave PCM disconnected.
Key on, engine off.
Measure resistance between PCM test pin 101 and ground.
Is the resistance less than 1 ohm? (Typical voltage should be 12 V.)

Yes - REPAIR short to ground in circuit 1086 (PK/OG).
RESTORE system. CLEAR DTCs and RETEST.

No - GO to QB10 .

 

Today I rechecked QB7 and QB8, both passed.
Tried QB9 by leaving GPCM unplugged and the PCM connected. KOEO and there was no continuity at all when trying to measure resistance. As for voltage it read 5.9v and no where near 12v with fully charged batteries.

I then moved to QB10. With GPCM plugged in and PCM connected, I unplugged the EOT and then hooked my meter to the 1086 wire just before the GPCM and engine ground.

With KOEO I was getting 1.5v and it would at times go up as high as 2.0v. Set my phone timer to 3 minutes and watched the meter the whole time. Just before the 3 minute timer went off the voltage dropped to .5v and stayed there.

According to the Test Procedure the voltage should have shot up to 11v minimum.
The sheet says to replace the PCM.

I also found the wiring circuit 1275 for my Wastegate Solenoid to be just fine. Continuity from the Solenoid plug wire (Wh/Rd) to the PCM plug pin #47 had zero resistance. With KOEO I can hear the solenoid cycling but I still get the P1690 failure code.
Would this also indicate a faulty PCM?

 

Went back to the beginning on the P0670 code and found that the my connectors at the valve cover gaskets had quite a bit of oil in them. Checked continuity on the GPCM harness pins and all checked out. Cleaned up the connectors and reassembled thinking I had found my problem.

Drove the truck for a few miles and then cleared the codes. Turned the key back on and sure enough the P0670 and P1690 are still there.

This is killing me!

 

Is it possible that the wire harness terminals at the PCM for those circuits are either loose or corroded? Could you have corroded or missing ground wires somewhere on the truck?

 

I have pulled, cleaned and inspected every plug in the harness.
In my GEM posting I took that module completely apart cleaned up the corrosion and put it back together. Right now I am getting no codes from the GEM or the ABS modules. Everything is concentrated in the OBDII and PCM with the main ones being the P0670 and the P1690. I have traced the wires all the way to the PCM plug.

I too have wondered about the bad ground somewhere but so far I haven't located or had a wire test as shorted to ground.

One thing I need to do is recheck the GPCM plug pins to ground resistance again. Since I cleaned oil out of those connections I may have been getting a false reading. Every glow plug lead came back almost exactly the same 13.0 to 13.2 ohms.

 

My GPCM does get warm when activated. Pretty sure that's why it's in a finned aluminum enclosure. Maybe in a cold environment where it was pumpin juice for a couple minutes it might get hot, but in CA it's mostly just engine room bling.

If it's not throwing a code, it's fine.

 

I ran the FORScan test for the Glow Plugs: KOER

(OK) [12:21:12.329] KOER Glow Plug Monitoring Self Test has been started
(WARN) [12:21:32.779] Test completed, found DTCs: P0640, P0683, P0670
===DTC P0640===

Code: P0640 - Manifold Intake Air Heater Control Circuit Fault

Module: Powertrain Control Module

Diagnostic Trouble Code details

Manifold Intake Air Heater Control Circuit Fault

This DTC may be caused by :

Open circuit.

Short to Ground

Possible causes are:

Harness wiring

MIAH Relay

PCM

Inspect connectors for signs of damage, water ingress, corrosion, etc.

===END DTC P0640===



===DTC P0683===
Code: P0683 - Glow Plug Control Module Communication Fault

Module: Powertrain Control Module

Diagnostic Trouble Code details

Glow Plug Control Module Communication Fault

Open circuit.

This DTC may be caused by :

Short circuit

Possible causes are:

Harness wiring

GPCM

Transmission Control Module

Note: Refer to the workshop manual for troubleshooting this DTC.

===END DTC P0683===



===DTC P0670===
Code: P0670 - Glow Plug Module Control Circuit

Module: Powertrain Control Module

Diagnostic Trouble Code details

Glow Plug Module Control Circuit

This DTC may be caused by :

Open circuit.

Short circuit

Possible causes are:

Harness wiring

GPCM

PCM

===END DTC P0670===

This the first time I saw the P0683 code, so I will double check that circuit.
Would this also cause the P0670 code?

 

Back to square one.
Pulled the driver's side valve cover and removed the UVCH to check continuity.
Everything checks out. There is one small crack in the wire casing to one of the injectors but the no breaks in the wire. I have read that synthetic oil is non-conductive so I am assuming this would not be causing any problems.

 

Try installing a temporary ground cable from the battery to the engine, to the frame and to the body. Make sure you have clean bolts going into either a cleaned out threaded hole in the engine or a sanded clean piece of sheet metal on the body and frame. A #10 stranded wire would be plenty large for this test. You can use any type of wire lug for this purpose.

There are ground connections under the PCM on the left side of your cab under the e-brake pedal. Check those connections for rust.

Have you looked at the PCM to see if a previous owner has installed a chip? If it has one, remove it to see if the symptoms clear up. Also look for water caused damage/corrosion on the PCM from a leaking windshield.

You could send in your PCM to a shop to have them check it for proper operation or have it reflashed at a Ford shop or dealership.

 

Thanks, I will give this a go today sometime.

Yesterday I pulled each valve cover and removed the UVCH to check them out with a VOM. They are fine.
Plugged the harness into the connector and then checked continuity to the PCM connector pins from each glow plug pin. Again everything checked out.
Pulled the 42 pin connector and checked continuity from #9 pin on PCM connector to the #24 pin. Again no resistance. I was hoping this might be what was generating the P0683 code.

Question: The power source for the GPCM seems to come from the Air Intake Heater solenoid. Is there a chance this solenoid may cause any issues/codes?

 

To keep this thread updated.
I took apart my PCM and cleaned it, then fabricated a grounding tab from some brass stock I had laying around.
Checked to be sure the PCM box was grounded, then cleaned battery grounds at the block, on the fenders & cowl, plus the under dash ground straps and the one near the PCM.

Today I pulled the UVCH connectors and the EOT connector. With KOEO I tested the voltage to each glow plug pin in the connector. All had just under 12v to them.

Installed a new EOT sensor and plugged it in. Rechecked the voltage and it was exactly the same.

I will attempt to clear the codes again and see what happens.