I'll try to make a long story short. I had the clutch changed a few weeks ago. Because of where I mounted the high idle switch down by the gear shifter I removed it. It's one of the first I switches I got it from DAP. I previously already changed the open wire in the harness because it started having problems. So back to this problem, I put the switch back in and the other day the IAT temps seemed weird on my scan guage 2 so I removed the switch to check it all out and make sure all connections were good. While doing this the power wire going to the switch for the indicator light came off. Me being the idiot I aim, I solder it back to the wires coming from the resistors. I checked everything else and it all seemed good. I put the switch back in, turn on the key, but did not start, check engine light came on water in fuel came on. So I took the switch out and realized what I did. I plugged everything back in without the switch, cleared the codes and started it, the water in fuel light is still on and codes po380 and 382 are coming up and I don't think my grid heater is coming on. So what did I do by sending power through the harness to the IAT water temp sensor etc? Where do I even start?

Edited November 9, 20195 yr by JAG1

I don't have anything helpful for you at the moment, but maybe check for blown fuses inside the truck and under the hood. I can't remember if both the ECM and PCM are fused in the interior. 

So now I have code po236 map sensor

First remove the switch reset the codes and make sure there is no IAT or ECT codes. If none are found then hook it back up and and test its function. 

 

As for the P0380 and P0382 those are grid heater solenoid issues or wiring issues to the grid heaters.

 

P0236 typically is a boost fooler issue your tuner isn't boost fooling correctly. If you remove the tuner and hook up stock again and the P0236 goes away then the tuner is at fault. That's if you have a tuner.

 

 

I checked fuses and relay in the fuse box and they are good. I don't have a boost fooler or any chip on it right now. The high idle switch is removed so everything is stock. Still have water in fuel light on  and code 236, 380, 382 and no grid heater. Runs fine, but idles a little high. I think I fried the computer.

Edited November 9, 20195 yr by JAG1

Maybe you just fried one of the sensors like coolant temp or IAT and the ECM is trying to offset it and that's why it seems to idle higher now.  You can try checking the senor readings at start up with a live data tool.  They should be close to what ambient temperature is when you first start the vehicle. 

If so then there would be a error code or the sensors will not match at cold engine key on. Just take a live data tool or Quadzilla key on and look at the IAT and ECT they should match or very close. Excessively cold ECT only sensor will change idle speed. IAT will do nothing to idle speed. IAT only controls timing and grid heaters. 

I only have a small suggestion..... to disconnect the batteries, including ground for about 30 mins. and turn on the ignition switch at the same time. Now I know I'm to be called a big donkey , but hey, it might help. It solved a weird problem once for me when wires got crossed up.

Edited November 9, 20195 yr by JAG1

Update.  Diesel mechanic narrowed it down to the ECM so we have ordered a new one. I don't think I'll be putting the high idle switch back on. Its basically the first generation switch I've had to fix wiring and stuff several times. The new switch looks like it's made alot better.