Hey all, I'm trying to t-shoot a hard start problem on my '88 LB9 IROC, (see: https://www.thirdgen.org/messgboard/Forum7/HTML/010748.html), and in playing with my Diacom, I came up with a couple of questions.

1) when the cooling switch is listed as ON, does that mean the ECM is looking for the fan to turn on? If so, why is my ECM looking to turn the fan on at 185, OFF at 190 and back on again at 187? Especially when the fans are turning on and off at just about any time they please.

2) Does the EGR Diagnostic Switch truly reflect passage of EGR? If so, why do I have 10 minutes or so of an ON condition, followed by about 10 minutes of an OFF condition? EGR Duty Cycle is doing its thing, but EGR switch seemingly isn't. Could it be a bad solenoid?

Thanks for the time, and if you have a chance, please check out my other post. Oh, and BTW, I originally posted this is the Gen Tech section, but it was suggested I come over here. - John '89 L98


[This message has been edited by John'89L98 (edited July 31, 2001).]

 

Anybody?

 

The cooling fan is operated by a switch on the head, not the ECM, so who knows what Diacom is reporting. The EGR diagnostic swith is a new one to me but it *may* mean that this is the time that the ecm will look for a fault in the egr circuit. In other words, if the egr circuit fails while the diagnostic switch is off, it won't throw a code but will when it's on. If the egr is working properly, I wouldn't worry about it.

 

Wrong again, this is about DIY Prom burning.