Originally Posted by Flares
I have a 2003 Winnebago Itasca Horizon (IKP34HD) with a 330 HP CAT Diesel (HEP20826). that will turn over when attempting to start but will not (start). Good batteries and connections all checked good. Additionally, there is a no yellow check engine light when the key is turned to the first (before cranking) position and the only gauges that energize are the air and fuel gauge. All the other normal just prior to starting warning lights illuminate fine. The (mobile) diesel mechanic that I use could not get his scan tool to "see" the engine to look at diagnostic codes.
His/our research determined that the engine ECM is either not getting power and or the engine ECU has failed. The mechanic went through all CB's and checked relays associated with the ECM and found them all good. Unfortunately, he has other scheduled jobs and will not be able to come back for a couple weeks.
Additional online research indicated that the electrical connector (to the ECM) should power to pins 52 and 53 (unswitched) and key on (switched) power to pin 70.
If you're still with me so far... 😂, My question is, has anyone here had a similar issue/diagnosis and eventual repair of the that issue? I would like to hear from you if you did. While the mechanic is out of pocket for a couple weeks, I'm probably going to check those pins for power before ordering a replacement engine ECM to get the ball (in this case the RV, 😉 ) rolling. Thanks for any pointers or advice anyone could provide.
I have never experienced this but have seen lots of posts that have. Incorrect or no voltages to the ECM do some strange things.
You say all the other instrument panel lights come on as normal EXCEPT the check engine light? That does indicate an ECM issue as that should light up anytime the ignition is on and the engine is not running. Mine, when I turn the key on ALL the lights come on, 30 seconds maybe if the engine is cold, air is low, etc including the check engine light. If I shut it off, after driving, all is warm, air is up jacks in right position, etc, and then I turn the ignition back on after say 15-20 seconds, the only light that comes on is the Check Engine.
Voltages do really weird things. Last winter, I would be driving down the road and all the lights would go into what they call a "Chase" pattern. Engine continued to run fine, no performance issues. I'd pull over, set the park brake and put in neutral and they would stop. Go back to normal. A couple times I did have to shut it off and restart. Researched and researched and everything always came back to a voltage issue. Then I notice that often, not always, after being parked for the night, I would get 20 miles down the road and it would happen. Someone suggested battery issues. When I got home I tested them all. Chassis batteries were fine but 2 house batteries were completely shot. One at 20% capacity and one at 10% capacity. PO had put a new one in and that one was good. As you know 1 good battery and 2 bad batteries = 3 bad batteries. I replaced all three with a matched set and good ever since. Came to the conclusion that upon starting, the alternator charged the chassis batteries first, then when they got up to voltage, flipped the bird and started charging the house batteries, which drug the voltage down and sent the ECM into the WTF mode causing the chase lights.
Good luck, Check all the pins for tight, clean with contact cleaner, if you do buy an ECM try and find one you can return if the is not the problem.