Strange electrical issue

[RDMueller]

A few days ago while driving, I noticed that the seat belt indicator was steady on with no chime even though I was wearing my seat belt. Additionally the radio wasn’t working even though it was on/powered (display lit, able to change stations but no sound). Got home and discovered the following also unpowered/not working:
Power windows,
Power locks,
Side view mirror adjustment,
Dome light with door open,
Chime with keys in the ignition or headlights on and the door open.
I checked all fuses and they all are good. From what I read on other forums, the IOD fuse (under the yellow guard) is often the culprit. It checks good, but I changed it anyway, still no help. I also determined that there is power going to that fuse (IOD). Kind of at a loss where to look next. Anyone else experience something similar?

 

[Ozymandias]

Check for the common ground. There is a good chance to find something rotten off. IOD is only for the remote and the radio stations.
If found the 2nd Gen always confusing to work on with its two fuse boxes.

 

[brucejohnson]

For troubleshooting purposes in using the correct schematics, what year and model is your truck?

 

[RDMueller]

For troubleshooting purposes in using the correct schematics, what year and model is your truck?

It’s a 2001.5 2500SLT

 

[brucejohnson]

It’s a 2001.5 2500SLT

Thanks. Should be close to the 2002.
Ozy's suggestion is the best starting point. According to the 2002 schematics, initially it appears to have the grounds G300, G301, G302 in common for most of your systems listed. Power comes from various sources so that eliminates that end of the circuit.
Now, just to locate those ground points. I'd start with the battery ground terminals.

 

[BigPapa]

I agree with BJ, probably grounds. If it was a 3rd Gen, I’d go straight to the TIPM…..

 

[RDMueller]

Thanks. Should be close to the 2002.
Ozy's suggestion is the best starting point. According to the 2002 schematics, initially it appears to have the grounds G300, G301, G302 in common for most of your systems listed. Power comes from various sources so that eliminates that end of the circuit.
Now, just to locate those ground points. I'd start with the battery ground terminals.

That makes sense. Battery ground terminals seem to be good, but I’ll check again. Now how would I locate G300, 301 and 302?

 

[brucejohnson]

That makes sense. Battery ground terminals seem to be good, but I’ll check again. Now how would I locate G300, 301 and 302?

G 300 - Left Lower Cowl (behind driver's footwell panel)
G 301 - Below Left Rear Speaker (in left body pillar where LR speaker wires come from)
G 302 - At Overhead Console (Overhead console - midway, upper cab? Hard to read the figure drawing)
With those locations being somewhat separated in distance, I would look for external body to chassis or battery grounds. That would include all three for the series 300 grounds making the circuit continuity back to the batteries from the cab.

No figure diagram for these:
G 115 (Diesel) Primary Battery Body Ground (At Primary Battery ground terminal)
G 117 (Diesel) Auxiliary Battery Engine Ground (On the 2002 schematic shows on Aux Battery GND)
G 118 (Diesel) Primary Frame Ground (On the 2002 schematic shows on Aux Battery GND)
G 120 (Diesel) Auxiliary Body Ground (At Auxiliary Battery ground terminal)

 

[RDMueller]

G 300 - Left Lower Cowl (behind driver's footwell panel)
G 301 - Below Left Rear Speaker (in left body pillar where LR speaker wires come from)
G 302 - At Overhead Console (Overhead console - midway, upper cab? Hard to read the figure drawing)
With those locations being somewhat separated in distance, I would look for external body to chassis or battery grounds. That would include all three for the series 300 grounds making the circuit continuity back to the batteries from the cab.

No figure diagram for these:
G 115 (Diesel) Primary Battery Body Ground (At Primary Battery ground terminal)
G 117 (Diesel) Auxiliary Battery Engine Ground (On the 2002 schematic shows on Aux Battery GND)
G 118 (Diesel) Primary Frame Ground (On the 2002 schematic shows on Aux Battery GND)
G 120 (Diesel) Auxiliary Body Ground (At Auxiliary Battery ground terminal)

ok, great. This definitely gives me some things to look at. Thank you!

 

[petersonj]

IOD is only for the remote and the radio stations.

On my '02, pulling the IOD fuse disables the interior lights, cargo bed lights, underhood light, glove box light, and some other things. The IOD fuse was introduced so new vehicles could still be moved around at the factory and dealer lots, but batteries would not be discharged when opening doors and raising the hood, etc.

- John

 

[brucejohnson]

If found the 2nd Gen always confusing to work on with its two fuse boxes.

And the data link/buss...
Don't forget to check BOTH fuse boxes.
Fuses 2 and 10 in the PDC.
Looking through the schematics and losing my sanity by jumping from indexes to descriptions, section to section and page to page and repeat and rinse ad infinitum, I have come to a couple other possible items.

• The CTM (Central Timer Module)
• Ignition Switch

Fuse numbers are listed in the 2002 manual and may be different for other years.

• Fuses 6, 11 and 13 (6 is powered via ignition switch in Run/ACC mode; 11 in Run/Start; and 13 is Battery - A7).
• Fuses 2 and 10 in the PDC

All 5 fuses feed the CTM.
Does anything on the list work in ACC mode?
Does the windshield washer function and the intermittent wipers do not?
The fuses do feed other circuits, some CTM affected and some not.

The reason I mentioned the ignition switch is the power windows and door locks are powered by the battery via Fuse 13 through the ignition switch and I did not find a direct operational link to the CTM other than the CTM receiving battery (mode) power.

 

[RDMueller]

And the data link/buss...
Don't forget to check BOTH fuse boxes.
Fuses 2 and 10 in the PDC.
Looking through the schematics and losing my sanity by jumping from indexes to descriptions, section to section and page to page and repeat and rinse ad infinitum, I have come to a couple other possible items.

• The CTM (Central Time Module)
• Ignition Switch

Fuse numbers are listed in the 2002 manual and may be different for other years.

• Fuses 6, 11 and 13 (6 is powered via ignition switch in Run/ACC mode; 11 in Run/Start; and 13 is Battery - A7).
• Fuses 2 and 10 in the PDC

All 5 fuses feed the CTM.
Does anything on the list work in ACC mode?
Does the windshield washer function and the intermittent wipers do not?
The fuses do feed other circuits, some CTM affected and some not.

The reason I mentioned the ignition switch is the power windows and door locks are powered by the battery via Fuse 13 through the ignition switch and I did not find a direct operational link to the CTM other than the CTM receiving battery (mode) power.

Fuses in the PDC are good. Wipers work both in intermittent as well as low/high. Windshield washer works fine. In ACC the radio comes on (still no sound) but nothing else comes on. But honestly I don’t remember what else should come on in ACC. I imagine windows should work in ACC, but they don’t. Locks should work regardless of key position and they don’t work in any position. I also checked both battery to chassis grounds and they look good.

I guess one thing that’s really strange is the radio (it’s an aftermarket Dual). It’s receiving power, it comes on and the LCD display looks totally normal, you can change stations, change the input/settings, change the volume, etc. But not ANY sound at all, no static, no hum, nothing! Makes me wonder if there are 2 power sources for the radio, one for the controls and a separate source for the amp? And it doesn’t have a separate amp I assume. To me, this makes a grounding issue seem less likely.

I’m usually pretty decent at troubleshooting, but this has me at a loss. Doesn’t help that I’m not great at reading those electrical schematics!

 

[brucejohnson]

Do you have the upgraded factory radio with the amp? Those have a choke that is controlled by a relay. If that is inop you have no sound. From the schematics it would seem the rear speakers would work, but it's hard to tell with the way things are controlled. I'll look at that troubleshooting description and schematic shortly as I just skimmed over it while looking for commonalities of the reported issues.

 

[RDMueller]

Do you have the upgraded factory radio with the amp? Those have a choke that is controlled by a relay. If that is inop you have no sound. From the schematics it would seem the rear speakers would work, but it's hard to tell with the way things are controlled. I'll look at that troubleshooting description and schematic shortly as I just skimmed over it while looking for commonalities of the reported issues.

No, pretty sure it wasn’t an upgraded stereo as it was quite basic, not even a cd player. It did have a tape deck though, lol. When I replaced it some years ago, I just bought a drop in replacement. I do think I remember having to wire up a harness, but that’s about it.

I did read that in that era it wasn’t uncommon to have an amp built into each speaker, so that might make sense as nothing electrical in the doors is working.

 

[petersonj]

@RDMueller , is your truck a Base, or Highline / Premium model? If it is the Base model, then the wiring diagram for the power door locks is straight forward. If the truck is the Highline / Premium model, then the door lock system runs through the Central Timer Module. More complicated to diagnose.

The power windows do not use the Central Timer Module on any of the models. This should be an easier circuit to diagnose.
Also, the fuse panel inside the cab in the dash by the driver's door is referred to as the "Junction Block" in the FSM. Not sure why anyone would think that would be a good name for a fuse panel.

- John

 

[brucejohnson]

No, pretty sure it wasn’t an upgraded stereo as it was quite basic, not even a cd player. It did have a tape deck though, lol. When I replaced it some years ago, I just bought a drop in replacement. I do think I remember having to wire up a harness, but that’s about it.

I did read that in that era it wasn’t uncommon to have an amp built into each speaker, so that might make sense as nothing electrical in the doors is working.

How about the steering wheel volume and station select buttons?

 

[RDMueller]

@RDMueller , is your truck a Base, or Highline / Premium model? If it is the Base model, then the wiring diagram for the power door locks is straight forward. If the truck is the Highline / Premium model, then the door lock system runs through the Central Timer Module. More complicated to diagnose.

The power windows do not use the Central Timer Module on any of the models. This should be an easier circuit to diagnose.
Also, the fuse panel inside the cab in the dash by the driver's door is referred to as the "Junction Block" in the FSM. Not sure why anyone would think that would be a good name for a fuse panel.

- John

It’s an SLT, not sure if that’s base or premium. It’s definitely above a tradesman as it does have carpet and cloth seats, plus in those days a base model probably had manual windows and no power locks. But I highly doubt it’s premium either.

 

[RDMueller]

How about the steering wheel volume and station select buttons?

Doesn’t have steering wheel volume or station select controls. Only cruise control (which is working).

 

[RDMueller]

Can’t believe I still have this! Should help with which trim level…

 

[RDMueller]

Ok, tried one more thing to try to narrow down whether this is a grounding issue or a supply issue. Dome light should be on any time a door is open, so I removed the dome light and checked for voltage, it was 0. Btw, I connected the negative lead of the multimeter to the negative battery post and then tested for voltage at each of the 2 wires not knowing which was the + or -. No voltage on either wire. Based on this, I’m guessing it’s not a grounding problem.