Can’t read codes no check engine light ?

[Problem Child]

My 95 6.5 4x4 Suburban was running so good and then she just died going down the road. I’m familiar with the PDM shutting down but usually she would crank back up. Mine is the updated Leroy driver and it’s located behind the front license plate.
This time she wouldn’t start back but would spin over fine. I had her towed home and was going to check codes with the jumper the next morning. The check engine light wouldn’t come on much less flash a code. I did smell a little burning smell after she died but couldn’t locate anything.
I’ve already purchased a new ECM but I’m only guessing that’s what is wrong. Before I install the new computer, is there anything I should check and do y’all think it’s the ECM at all ??

 

[NVW]

The light likely just needs a bulb. I would check all the fuses, esp. the FSOS in the engine bay fuse box. My 95 would lose contact and it would shut down like the ign. was turned off.

 

[dbrannon79]

are the glow plug time circuit functioning? that would be an indication the ecm is working or not. I have never had any luck using the jumper wire on mine reading codes. I had to invest into the GMTDscan software in order to read codes. iirc the two pins on the diesel are the furthest right side top and bottom pins to short unlike the gassers would be the top two right side pins shorted to read codes. at least on my 95 I have to connect my homemade usb cable to those top and bottom pins for the laptop to connect to the truck.

 

[MrMarty51]

Did You try a known good or new PMD ? the thing behind the license plate.
That would be the very first step that I would take. A bad PMD wont always restert the enjun once it has failed and after it has cooled down.
Fuel pressure could be an important factor too.

 

[WarWagon]

The check engine light wouldn’t come on much less flash a code.

No WTS, STS (throttle), and No check engine lights? Likely no power to ECM. Check fuses and fusible links. Check grounds including the 1-3 wires by the transmission dipstick as one of them is the ECM ground. Check batteries, separate and load test, in case one failed.

Yes it can be a bad ECM. Yes something could have shorted out and taken out the ECM (Not likely). Verify power and consiter the age of fuses and fusible links are suspect as an age failure alone. Inspect wiring esp under the intake and by the starter if you pop more fuses or fusible links.

 

[Problem Child]

I’m working every day so I’m taking this kinda slow. Today all I did was charge the batteries back up and kinda just looked around for something burnt or melted. I do remember smelling a burnt smell from under the hood. I also checked all fuses with an ohm meter and all seemed fine.
I have an official shop manual I purchased for $15 when a local dealership shut down. I’m in the section about no Service Engine Soon light and this should really help. I have probably a stupid question but where is the continuous battery fusible link located, and is there one on each battery? Thanks

 

[dbrannon79]

for yours, I don't think there is a fuse link that is for the main power. it should have "maxi" (large) blade fuses in the relay box under the hood. I may be wrong though. you could however pull the clove box and unplug the ecm use a test light on the ecm connectors while using the schematic in the service manual testing for all power and grounds that go to the ecm. if you find any that is missing power. start looking at that circuit in the diagram where it gets power from. could possibly be a burned contact in the ignition switch.

 

[Problem Child]

Today I got around to checking a few circuits for no SES light. I checked the CKT 440(battery feed) and CKT 439(ignition feed). Both were good. I then checked circuit CKT 419(SES control), with no power there.
I went ahead and pulled the instrument cluster and sure nuff the SES bulb is blown. So will hopefully replacing the bulb correct the no voltage to the CKT 419 circuit ??

 

[MrMarty51]

Thats a bit of a good diagnostics right there.