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Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 4869
Experience:  Owner at DJ Wilson
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Crank no start, VT365 with DTC 543, 2007, ic school bus with

Customer Question

crank no start, VT365 with DTC 543
JA: What's the make/model/year of your truck? Engine type?
Customer: 2007, ic school bus with VT365
JA: Are you fixing your truck yourself? What have you tried so far?
Customer: checked wiring from ECM to IDM, tried different IDM, checked power from battery through relay to idm
JA: Anything else you want the truck mechanic to know before I connect you?
Customer: no
Submitted: 1 month ago.
Category: Medium and Heavy Trucks
Customer: replied 1 month ago.
no injector buzz when turning on ignition, I tried a known good IDM from a different bus and it did the injector buzz for a few seconds slow and then then quit and won't wont work on the other bus anymore.
Expert:  Daniel Wilson replied 1 month ago.

Hi my name is***** with me while I pull up some info on your code.

Expert:  Daniel Wilson replied 1 month ago.

543 — PCM/IDM DTC 543 is set by the • DTC 543 can be set If IDM power is low, DTC
Communications Fault PCM when the PCM is not when the CAN 2 lines 543 can be set.
communicating with the between the PCM and
IDM. IDM are shorted to
ground, VREF, battery or
the current is open.
• When DTC 543 is active
the amber ENGINE
indicator is illuminated

Expert:  Daniel Wilson replied 1 month ago.

Check the fuses and relays for the IDM as well as for problems in the wiring harness/connectors.

Expert:  Daniel Wilson replied 1 month ago.

Check in the Battery box for an ECM/IDM inline fuse and inspect the wiring as well. Let me know

Expert:  Daniel Wilson replied 1 month ago.

Since it now wont work on the other bus I would be concerned about a short in the wiring damaging the IDMs.

Customer: replied 1 month ago.
All fuses and relays are ok. I've checked the wiring for short to ground and I can't find anything.
Expert:  Daniel Wilson replied 1 month ago.

Thanks for the info. Monitor the voltage to the IDM and check the charging system as well. Make sure you have no voltage spikes or issues. Let me know

Customer: replied 1 month ago.
The voltage to the IDM is good and I can't check the charging system since it won't run. No voltage spikes without it running. The vehicle came into the shop running and just wouldn't start initially.
Expert:  Daniel Wilson replied 1 month ago.

Thanks for the update. The other IDM failed with just the key switch on or after trying to crank the engine over? I ask because I am concerned with a short. if not in the wiring harness or bad main ground, you could have a shorting alternator, shorting starter, ignition switch, possible internal battery issue. The battery can be tested with a digital tester for internal issues, the starter and alternator can be bench tested. The wiring harness and be inspected and continuity checked with an OHM meter including grounds.

Customer: replied 1 month ago.
I've checked the harness with a ohm meter and checked for shorts to ground on every wire, the ground wires and power wires area all good. The pin 7 on the idm (ign feed) has continuity to ground until the ign switch is turned on and then there is 12v power. I've replaced the batteries, and cleaned the terminals.The other IDM did the inital injector buzz but slower than it should have on the first 2 ignition cycles but the engine wouldn't start. On the 3rd cycle it wouldn't buzz anymore.
Expert:  Daniel Wilson replied 1 month ago.

Its possible the other IDM failed at that time but Id be leary on trying another one if there is a short or backfeed frying the IDMs in the circuit somewhere.

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