M978A4 HEMTT going into high idle

SSG Private RallyPoint Member — Thu, 28 May 2015 16:14:23 -0400

I'd like to know if anyone has had any issues with a M978A4 HEMTT going into high idle or why you go to engage the high idle in the back when you are pumping fuel and it won't idle up. Then when you look that the panel in the cab and the high idle is lite but it's not turned on.

Response by SGT Heath Johns made Nov 17 at 2016 11:57 AM

SGT Heath Johns — Thu, 17 Nov 2016 11:57:20 -0500

Had issues with this in Germany, once the A4's took over our mechanics were on over drive trying to break this issue down. Ended up being the switch. Not sure if it was contacts, or wiring, but that'll be your source. If nothing there, check the throttle plate and wiring to see if something is wrong there.

Response by SGT Private RallyPoint Member made May 23 at 2017 10:15 PM

SGT Private RallyPoint Member — Tue, 23 May 2017 22:15:12 -0400

Double check to make sure transmission is in neutral. If it is in gear, high idle will not engage from the rear of the truck even if switch in cab is on.