High idle can't be set higher than 1200 rpm?

[wheelcheck]

I have a 2007 258LP with a rear load garbage body on it. One day, the high idle for the hydraulics drops from 1500rpm to 1200rpm. Brought it to the dealer and he says every time he tries to set it to 1500, it auto corrects to 1200 and it won't let him set it any higher. Has anyone had a similar experience with this. I have 5 or 6 of the same exact trucks and all their high idles are set to 1500 with no issues.

 

[Hino123]

Never had an issue here, never heard of such and issue. You have to do it properly when programming or it wont take. Could possibly be a Allison issue but doubtful. Is the dealer/tech knowledgeable? He should have opened a tech assist case if he cant figure it out. PM me your vin. I can take a look as see what it is set to.