Any help on this would be appreciated.

I have an early ‘99 PSD F250. I’ve had a service engine soon light on for a while (this is not my daily driver). I tried to read the codes multiple times but no scanner was able to retrieve codes from the OBD port (even the Snap On scanner would read ABS and airbag, but not PCM). The truck drives the same as the day I bought it - no weird idle, starts fine warm or cold, no change in fuel efficiency. Just drove it on a long trip to move my son back from college with no issues. The SES light will go away for a short time after hard acceleration (passing on freeway), but comes back soon after.

I need to get a CA smog (please no rec’s to move out of CA - I would if I could) and the SES light is an automatic fail.

I finally bought a good Bluetooth scanner for FORScan and I was able to read the following codes:

PCM: P1316 Injector Drive Module codes detected (would the truck drive fine with this code?)

GEM: a bunch having to do with 4x4, even thought the truck seems to go into 4 wheel drive no problem (manual hubs and shifter). The high and low lights on the cluster light up as expected.
P1812 - 4WD drive mode select circuit failure
P1828 - transmission transfer case high to low shift relay coil circuit failure
P1820 - transmission transfer case low to high shift relay coil circuit failure
P1876 - transfer case 2WD solenoid circuit open or short to ground
P1832 - transmission transfer case 4WD solenoid circuit failure

 

I would start with deleting the codes, and see what comes back.

 

Already cleared all the codes. These are the persistent ones that came back.

 

Check for a bad ground near the t-case. You're getting a lot of electrical fault codes related to the t-case, so you've either got a bad ground/wiring or an entire wiring harness is disconnected.

 

OK. I’ll check tonight. Thanks.

 

Under what classification is CA smogging this? The early ones like '99 were sometimes classified as OBD-I but I don't know if this even matters for the diesels?

 

Not sure what you mean by what classification. Beginning in 2010 all diesels 1998 or newer <14k giver require smog check, no dyno or tail pipe measurements, just MIL check, visual inspection, and look for smoke. Smogs weren’t required when I bought the truck - several years later it became a big deal, especially for people who did Banks upgrades to their exhaust or chipped their PCM.

 

the grounds I have found look fine, but are dirty. How do you guys clean the grounds? Disassemble, wire brush, light sandpaper. Do you coat them with anything?

so far I found a strap passenger side near the transfer case body to frame rail, one strap in the engine compartment passenger side, another on the passenger side maybe 2 AWG to the back of the engine. I don’t see anything near the back of the PCM. Can anyone point me in the right direction for what I’m missing?