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Engine/Transmission (1998.5 - 2002) No wait to start light. Bad ECM?

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I went to start my truck the other day and when I turned on the key the wait to start light didn't come on and I didn't see any draw down on the volt meter from the grid heaters either. I waited the normal amount of time it takes the grid heaters to cycle and then tried to start it. It turned over real easy but it wouldn't even think of starting, it was about 15 degrees at the time. Turned the key on and off a couple of times and tried it after having let it sit for a while and still no wait to start light. It got up to 35 degrees today so after work I tried it again and even though the WTS light didn't come and the grid heaters didn't cycle it did start after it cranked a little.



Does anybody know if this is caused by a bad IAT sensor or is the ECM bad? I seem to remember the WTS start light always coming on even if it only was for a second or two even when it was hot out.



Thanks !

Chris
 
The WTSL H A S to come on!



You could try this one.

Disconnect both positive battery cables for about an hour.

Now, before you re connect the cables turn the key into the run position.

Re connect the positive cables. ( With the key in the run position)

The WTSL should work now, otherwise there's a problem with the ECM.



Marco
 
Positive cables??

Marco...



When I lost my WTS, at your suggestion I disconnected the negative cables, which fixed it. Maybe you told me positive, and it just didn't register. Not a slam... . just asking to clarify.
 
Yup, that's correct, I said negative cables.



Later, thinking about it more...



The ECM has two different power sources. One that's always hot (12 volt).

The other is hot only when the key is in run position.



That's why I say to turn the key into the run position before re connecting the batteries.



That way the ECM has to do an complete reset.



Oh, yeah, BTW, no matter which side ( + / - )we open in a DC system. No juice is no juice... :D



Marco
 
Its Back!

Thanks Marco that did the trick. WTS light is back and the grid heaters are working. One thing I do notice is that even after it is up to temperature and I shut it down as short a time as five minutes it still takes the same amount of time for the WTS light to go out. Is there something else wrong? It seems to me that when it used to be warmed up and you restarted it the WTS light went right out? Is the IAT giving the ECM the wrong values or do you think there is something wrong with the ECM? Thanks again Marco!



Chris
 
That's not an ECM problem.



The ECM does only what it's told to do via it's sensors.

Could be an dirty/bad IAT.

Maybe it's just really cold?



Marco
 
The battery disconnect also fixed mine. (disconnected for less than 2 min). The question I have is why are the catcher ECMs' needing to be reset. I had over 80k on my stock ECM and didn't have to do this. Is there ram in the ECM? Is the new program not clearing old data for peak values? I'm just curious why this should have to be done. Marco, I PM'ed you awhile back but didn't get an answer about the difference between the Ca. SO and the national SO trucks. Hope to hear from you soon. Mike
 
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