Fault Code 17 (data exchange problem) & Dealer B.S.
 

My own personal “onboard diagnostics” detected a fault code – “B.S.” arising from the dealership service writer.

On a 1994 E420 (124 w/ M119 engine, 88,000 miles) :

I just had the infamous wiring harness replaced (along with the Mass Air unit and few other non-related items) & I specifically asked them to give the throttle slide assembly a good looking over while they were in there – they said it is O.K & sent me along my way.

The car ran GREAT. For about 6 miles. Now, fault code 17 is popping up again, and the dealership service writer says that it is caused by a vacuum leak. Give me a break – code 17 relates to a data exchange fault between modules, but I’m not sure which specific modules, or if this is a general code that requires further investigation to determine which module is having problems communicating. (Throttle slide, anyone?)

Anyone have any comments about this? Please let me know what you think! I’d really like to be barking up the right tree… And maybe, just maybe, it could be caused by a vacuum leak – although I strongly suspect that is not the case.

RTH

It will idle rough if it is a vacuum leak.

The testing for this CAN code includes unplugging theDM and reading the resistance between CAN L and CAN H. In further tests it looks at the CAN element in the engine control module (N3/4) and separately the CAN element in the EA/CC/ISC controller.

I agree that vacuum leaks aren't part of the problem. Reset your code and see if it comes back.

DTC 17 for Diag Module
 

is, as you say, "Data exchange fault between individual control modules".

Also DTC 17 for the LH-SFI Module is "CAN data: Elec Acc Module - no data transmission". So suspect the new harness is not guite right especially if it worked ok before the harness swap.

With an ohmeter, remove the Diag Module, then check the resistance between the TWO WIDE PINS; sb 60 ohms +/- 5.

Pull out the LH-SFI (N3/1) module, then check the resistance between the TWO WIDE pins; sb 120 ohms +/- 5.

Then check that there's continuity between the corresponding pins between the two modules. Most likely one or both is not making. That's due to the wiring harness 'replacement'.

This I understand, and am having the same 17 blinks on the DM

Now this is confusing, because the DM is port 19, but the LH-SFI module is port 4. I take it the info below refers to 17 blinks on port 19 of the 38 pin socket, NOT the 17 blinks on port 4

Trying to figure out the 17 blink port 19 Diag Module issue.