w639 circuit 87

[GazPB]

Right, after jump starting the van with reverse polarity (not by me) the AA said the ECU was fried, so of it went to be repaired....It never came back (different story) so a ECU kit was purchased on eBay, fitting went well until it was realised the Speedo was different, mechanic I bought it off said this would not matter.
Anyway... Van won't start.

Diagnostic reader won't connect with the ECU. (Icarsoft)

Have checked all fuses with multimeter.

Things I have found is that there is low voltage on the fuses No. 8,9 & 10 to terminal 87and fuses No. 40 & 41 (engine fuse) all coming in at 0.25v

Battery is charged.
When inserting key, the steering lock releases and when key turns to start. Nothing.

Any help will be gratefully received.

 

[grober]

Most modern Mercedes have a "prefuse" power distribution unit which has fuseable links [large capacity bolt in fuses] which in turn supply the various fuseboxes/permanently live connections. Sounds as if the reverse polarity may have blown some of these fuseable links [ what they are there for]You maybe need to find the prefuse location- no idea where that might be on your vehicle.

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies