PDA

View Full Version : Volvo B12M



renesis
8th March, 2011, 03:57 PM
Hi, I have a Volvo B12M bus with D12D engine, Knorr EBS, Knorr ELC, EGS gearbox.

I am unable to start the bus with the ignition key switch. The ignition switch is working well as it is connected to the VECU showing the correct signal when turned to "start" position.

If I short the starter motor the bus can start, or if I short the IOA module ( a certain pin ) to 24V I can start the bus.

The following are the items checked
1) Rear start (engine compartment start) - all functional
2) Neutral gear position sensor - functional and correct
3) Ignition switch is fine
4) Relays are all working fine
5) Supply +30 and Ignition 15 are all ok
6) CAN J1939 and J1708 lines are all connected well with no breaks

I have tried connecting VCADS to this vehicle,but am not able to get any information. VCADS hangs at "Collecting vehicle information... 30%". It seems as though my VCADS cannot access all the other ECUs (including EECU, EBS, ELC, VECU..etc)

The funny thing is, I can view the ECUs' ID and part number through the instrument cluster.

Another same vehicle B12M (same specs) I have no problems with VCADS identifying and diagnosing it.

What other checks should I perform?
Any advice will be greatly appreciated.
Thank You

dieselequipos
10th March, 2011, 12:43 PM
Hello friend

check a 1708 communication, because , you could see on screen normal but on diagnstic software no. i think problem on 1708 check.

renesis
11th March, 2011, 08:29 AM
hello ,thank you for your information.
Today I managed to start the bus, the EGS control unit had some problems.

But in VCADS, I can only see MID 164 ( Chassis )
, cannot see all other Ecus like engine 128, vecu 144..etc
How should I carry on checking? Do I check for continuity between the J1708 wires from the other ECUs to the diagnosis socket or?

dieselequipos
12th March, 2011, 01:38 AM
yes is correct idea , check this conection to diagnostic socket

howabout
12th March, 2011, 01:58 AM
hello friend, since I had the same problem as you report and the failure was in the transmission control unit, which was the link with the transceiver j1587/1708 damaged leaves. in fact it was causing noise in the data link. You can test the control units individually, and check the level of tension between the orange wire and ground and then between the gray wire and ground. You can also use the Vcads as a means of communication or even use your own dashboar