Correct ECM (Cold Start Module) For 1990 Truck
 

I have a 1990 auto trans VIN 1B7KE2683LS605089. I am having issues with intermittent cycling of the grid heaters. Ran the Alldata test protocol and it seems to indicate a bad controller. Harness seems OK by visual inspection and sometimes the heaters will cycle correctly. Can anyone provide any insight? Also, the correct ECM for this truck is....? I need the one that works at 59 degrees. Any help appreciated. Thanks.

welcome to dtr! No ecm in a 90, I don't think. There's a little black box on or near the firewall that runs the grids, iirc. I'm a little out of the 1st gen loop, so I could be way off base. Someone smart will be here shortly, lol! What are the symptoms?

That little box located below the brake booster is what is giving the problems.

Maybe you should check your intake temp sensor. ECM's rarely go bad. If its not receiving the correct input than your output will not be correct. Just a thought. I'm not real up on how the grid heater system functions because i've never had a problem with one.

I have swapped out the temp sensor ( thermistor) and the system behaves the same way.

Grid heater control module or Cummins calls it Heater Control Module, it's on the drivers side firewall.

About 3 years ago I had the problem where the intake heater would work sometimes, after checking all of the parts before and after the ecm it ended up being the ecm. I found a used one on the internet 150.00. Check and make sure everything is grounded well.

The old 15 degree controllers are superseded, you won't get one of those.

I knew I had researched this recently, but it took me a while to find it.

See:

https://www.dieseltruckresource.com/...79&postcount=4