DC-link discharge failure
• Check for DTC's from the MGS that could explain the DC-link discharge failure. If relevant DTC is present follow the instruction for that DTC. If no other DTC present perform the following. • Try start up and shut down the system and see if the DTC is set again • Read out the DC-link voltage and battery voltage via SDP3 and see if they are equal. It shouldn’t differ more than 4V • If the voltage difference are less than 4V and stable. Change the BDU according instruction in Multi. NOTE! Replacing the BDU is considered an electrical work and shall only be performed by Scania certified personnel. Vehicle shall be made safe according to electrical work procedure. • If the voltage difference is larger than 4V and slowly decreasing with 30V/15min change the MGU according to instruction in Multi NOTE! This is a damaged MGU and there are risk for electrical hazards when performing this job and shall only be performed by Scania certified personnel. Vehicle shall be made safe according to electrical work procedure.
What you'll see
No driver-visible symptom recorded.
System reaction
No problem in the system during operation but the fault must be handled since there are risk that the safety functions in the system does not work. During service extra precaution must be taken from the beginning of the electrical work since it is work with voltage.
Diagnostic depth
After system shut down request there are still voltage on the DC-link.
The contactors are welded and can’t disengage the system or the discharge circuit in the MGU can’t drain the energy left in the X-capacitor in the MGU.