I have a 1999 Dodge Cummins 24 valve. It's suddenly hard to start so I checked the codes. I got 380 & 382, so I checked the relays and it's not getting ignited/excited on the heater side when I turn the key on.The battery side of the relays are hot. I used a jumper wire and manually applied them, I can hear them click on. The diagnostics in the scanner say to do this to see if the relay is bad, if not then it just refers to the ECM. Is there an air intake sensor that can go bad? If so where is it and how do I diagnose it.Is there a way to positively diagnose an ecm?

IAT sensor controls the grid heater you can test it by reading error codes and by using a live data tool like a ScanGauge II. 99% of the time the IAT is just fine but the relays are known to fail... Check the to light gauge wires for voltage and then check them back at the ECM for voltage too...

IAT sensor controls the grid heater you can test it by reading error codes and by using a live data tool like a ScanGauge II. 99% of the time the IAT is just fine but the relays are known to fail... Check the to light gauge wires for voltage and then check them back at the ECM for voltage too...

The relays work when using the scanner to manually operate relays. There is NO voltage to any of the relay contacts,except the 2 heavy wires on the battery side, it acts as if the sensor isn't sensing the cold, or the ecm isn't instructing the realys to activate. I need a way to check the sensor and ecm? I think I've checked everything else.

It so I would use a live data tool like ScanGauge II to verify the IAT temps. Grid heater are not enabled till about 60-65*F and colder. So getting a live data tool and checking would tell you a bunch...

It so I would use a live data tool like ScanGauge II to verify the IAT temps. Grid heater are not enabled till about 60-65*F and colder. So getting a live data tool and checking would tell you a bunch...

I used Snap - On's best live scanner, came up with same codes, which say that the problem is either the relays or pcm. I replaced the relays and the PCM was going to be next. Luckily I had left the truck run for 30 minutes in one place and noticed a drip of fuel on the ground. Inspection with a mirror revealed a pin hole in the return line from the injector pump, causing me to loose my prime, making the truck hard to start in cold weather. The leak sprayed onto the block and really never made it to the ground while moving. Scanners don't show mechanical problems like leaks, so they diagnose problems as electrical or computer. Anyhow, $87.00 for a new line was a lot better than a new pcm.