OK i have had some trouble with a few (2-3) buses in the past year do this to me.. its a 29 pass with the VT365..what happens is the bus will run like garbage and have a miss on 1-3 cylinders and a code 525 after and hour of idle and running around the lot, i run the tests and they straighten up and the miss disappears, and then its fine. they take it out for a while and it does the same but diff cylinder(s). then ill get an idm relay voltage low..i change the relay and tear all the wiring out checking for an obvious break in the wiring.batt voltage is fine too.. no problems found.. then on IKNOW they have an article for a lower computer replacement that doesnt needs to be programmed... anyone have any luck with the revised lower half computer part they offer?
We had a bus last month with a 525 that wouldn't go away. After much testing it was found to be corrosion inside the battery feed wire at the connector. Have not used an IDM bottom kit at this time.
Saw the bulletin but haven't tried it. Prior to this, we drive it to our dealer and change it in his parking lot and then have them reprogram it while we wait. Remember to get them to custom program your low coolant sensor (if that feature was added during the campaign). But it sounds like bad IDM is a good possibility. Did you check inside the connectors in the battery box real good. These are notorious for melting as well as the connector about 5 or 6 feet up the line. We have had the most problems recently with the IDM relay bases on the firewall melting. Standard S803 is a good replacement for the base as the pigtail has heavy wires. Swapping your IDM with one from another bus could be a good test too. We change the whole ECM/IDM assembly as it is fairly easy to make a quick swap and test drive without even bolting it all the way in. Good Luck.
i pulled the whole 6Ft of cable from the battery box for the idm ecm power and ground wires and connectors for chaffing and melting...nothing found...i also put the revised harness for the top of the batteries and double checked that.. nadda.. turned out it was the lower idm...didnt need it reprogrammed for the low coolant so it was perfect right at our shop! thanks again!
Code 525
Posted - 05/25/2012 : 09:29:40 AM
