New member/first post. Apologies in advance for the length.

My grandson just got a "new to him" 2005 1500 ST, 4.7 with the Getrag 238 6-Speed. Lots of issues that we're trying to get sorted, but let's start today with electrical.

NOTE: I have verified that Fuse 51 is in place and not blown. A visual inspection underneath the IPM doesn't find any obvious bad wires/connections. With the fuse in place, there is a constant "buzzing" in the instrument cluster. If the fuse is removed, the buzzing stops. If I plug in a scan tool into the OBD2 port the buzzing stops, but the scan tool doesn't work. If I turn the key to On, the buzzing also stops.

Symptoms:
- OBD2 port is not working
- Radio not working
- Wipers wonky (don't return to park position, don't always turn On / Off, Intermittent only works intermittently [lol])
- Probably other issues, but can't keep track of them all!

Ran cluster Actuator Test and get the following C Codes:
- 01 38
- 05 35
- 26 35
- 39 35
- A3 02

I have the list of failure messages so I know what each of these codes descriptions state. For example, I know that the code "01 Cargo Lamp LED output circuit load/short to ground" has occurred 38 times, However, because the OBD2 port doesn't work, I can't actually use a scan tool to diagnose any other issues.

I can't figure out where to go from here and I'm looking for some help on the best way to troubleshoot. I suspect I've got a short or bad ground someplace but in the few days that we've had the truck I've been unable to find anything.

~John

 

You never know what previous owners did in 17 years.
My first thought is that you have a ground problem. Erratic electrical and buzzing is often ground related.
I rec check your grounding wires/straps for flexibility, and ensure the attachment points are clean and tight.
As a test, you can read your battery voltage at the battery terminals. Leave the probe on the positive terminal and put the negative probe on a clean metal part of the engine. The voltage should be the same as the battery voltage. Do this check with as many grounding point as your probe will reach. Also check the ground at the fuse box.
Is your radio stock? You may want to remove the radio and see if there is improvement.
Your battery should read at least 12.5v static and 13.5v with engine running.

 

Thanks for your input!

It turns out that there were two problems:
1) The connector at the bottom of the IPM that included fuse 51 had some corrosion and was putting out weak and intermittent voltage on the wire. Cleaned this up and voltage on the wire is now a steady 12 volts.
2) The splice (S304) in the wire from Fuse 51 was bad. This splice leads to the OBD2 port, the instrument cluster, and the radio. I was getting 12 volts on wire from the IPM all the way through the firewall and into (and out of) connector 219. But none of the devices on the other side of S304 were getting 12 volts, Because the splice is inaccessible without removing the dash, I instead just added a new splice. Problem solved.

I did check all grounds (that I could find!) and some looked a bit sketchy so they have been cleaned up.

~John