Help! My intermittent start failures - Page 3

another problem.

lets start from basic...

desynchronize system with HHT (hand held tester) and then resynchronize all infrared remote control keys for this vehicle.

possible problem is timing with transponder at CAN (controller area network) interface.

you really need to have a diagnostic computer in this case. i need the fault code as well.

quote:

it is possible for the CPS to be faulty, but some tell-tale signs contradicts it such as: the flashing of LED on the mirror and the fault code which is not present.
it's just so un-convincing.

1. What's a CPS?

quote:

possible problem is timing with transponder at CAN (controller area network) interface

2. How do you justify if the timing with the transponder at the CAN is not accurate? It seems that the replacement of an IFZ Control Module doesn't seem to rectify the problem.

CPS - crankshaft position sensor.

the timing to CAN is interrupted by the interior motion sensor.
he got a different car and system. it can't be the same with yours. he might end up replacing the control module... or already did. i can feel his car is okay now, and just trying to get some answer...?

Thanks much for the qucik response SleepWalker, I don't have HHT but when I called benz road side assistance. Technician brought computer with him, he hooked up wih the car but it wouldn't read it. It would say turn on the ignition when the ignition is already on

please check the fuse number 17. was it okay?

on the diagnostic socket, was there a power on pin number 3 with ignition "on"?

Does a faulty MAS (Mass Air Sensor) contributes to intermittent starting failures?

no.

the car have emergency or "limp home mode" function.
the check engine light will be "on".

the car can still start and be driven even without the air mass sensor. during this operation, the engine control unit will adjust the injection time according to the position of throttle valve only.

Hey Sleepwalker,

1.Just referring back to your old post, the red circled portion--> Control Area Network

2. Ok, the IFZ and the ECM are new. There seems to be a signal interruption whenever i fail to start my car.

3. Just one question, the transmission of signals in the CAN between the IFZ and ECM, are there wires connecting between to these 2 control modules for the transmission? If yes, i think i would request the technician to unplug and replace the wires, maybe it would work?

This is because when the 2 control modules were being replaced respectively, maybe the wires connected to these modules (if there are any) were being slightly tampered even so that the car could start, but sometimes the signal may be interrupted. Just thinking aloud.

cheers


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yes. there is two wires for CAN-bus.

CAN low is green and CAN high is white.
you can see it from the wiring diagram i sent previously.

am afraid the wire just for CAN-bus cannot be replaced separately because it is together with the wiring harness. unplugging it is possible for testing purpose.

now you are planning to give the mechanics an instruction on how to do the job. i think they have all the advantages compared to us because they have all the knowledge and equipment to explore all possibilities... not to mention that the car is all on their hands now.

checking all the connectors is a good idea. presence of dirt or oil on other control unit that uses CAN will surely affect all. have the other control unit check as well for good connection and cleanliness.

just a small idea: if either one of the CAN is disconnected or grounded, the other CAN will automatically take over. the faulty CAN will be disabled by the system and a fault code is put into memory. if there is something that disrupts the two, then that could be the culprit.

so once again, just advise them to check well... CAN included.

quote:

if either one of the CAN is disconnected or grounded, the other CAN will automatically take over. the faulty CAN will be disabled by the system and a fault code is put into memory. if there is something that disrupts the two, then that could be the culprit

Hey sleepwalker,

I still need your help and comments on my 1995 w202. The dealer has made some changes to the settings/ codings in the ECU and it still did not solve problem.

It happened again right after I was about to collect my car from the workshop.

Any ideas?

it has nothing to do with the coding, programming, and settings.

it is still a component/signal problem which can be detected when the problem is present, according to the fault code, and actual values.

it happens after they change you engine control unit, so they must have installed a defective parts.

it is still under parts warranty, and they must replace it for the benifet of the doubt.

quote:

ORIGINAL: sleepwalker

it happens after they change you engine control unit, so they must have installed a defective parts.

it is still under parts warranty, and they must replace it for the benifet of the doubt.

Ok, have you heard any recent news lately any recall of manufactured MB computerised parts this year?

only on electricals:

163, 210, 129, 220, 203, 215, and 208.4

just curious - what was for 129? Thanks.

only for electrical group. service measure includes many groups and depending on the production time.


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Hey sleepwalker,

Referring to the highlighted circle result, does this message always occur whenever there is a fault in the IFZ control module signal transmission or some other areas in the CAN?


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no. but the other one...yes.

on your car, only HHT function can be use for diagnosis, and i find it strange that the HFM cotrol unit detects the fault from itself and not from other CAN consumer/user.

internal fault???
HFM???

weak semi-conductors such as resistor, capacitor, condenser, diodes, and transistor cannot be avoided sometimes. but if it does, it must be faulty all the time.

the big question now is... under what certain circumstances that the problem occur?

temperature?
operation?
parking angle?
the way the car was stopped, locked, door closed?
barometric pressure?

it is very difficult. something must have affected something.

simulating such influencial parameter is very hard because we don't even know what it was. it can be anything.

the fate belongs only to the hands of the technician now who got access through all of those.

Sleepwalker,

Does a failing OVP relay affects the transfer signal from the IFZ control module to the HFM during ignition/ starting?

Thanks!

am not sure if your car uses OVP or base module because it is a newer model.

i think no.

As a matter of fact, my unit has an OVP relay

the dealer had just replaced a unit for another 1995 C280 who did has the same symptoms as mine. That car has not returned for a complaint for 3 weeks but I am not sure whether the OVP relay replacement did solve the problem.

Well, I hope this attempt will make a difference..

if yours got an OVP, then it's worth a try.

the part is relatively not expensive. you can use it for test purpose or simply replace them.

quote:

if yours got an OVP, then it's worth a try.

the part is relatively not expensive. you can use it for test purpose or simply replace them.

Thanks for the reply sleepwalker,

well the ovp replacement did not solve the trick, the damn problem happened again two days later after installation.

Now they are trying to replace a new wiring harness, that's the final solution.

The wiring harness is the CAN Bus controller right? This harness does the transfers of signals from the IFZ to the HFM right?

yes. the CAN BUS goes by wire.

but i still stick to the version where the problem only happens after the engine control unit was replaced.

Thank you for your reply sleepwalker,

Somehow I agree with you that it may not be necessasry to replace the existing wiring harness.

But it is still part of the process of elimination and I would not take the risk of applying this replacement.

I hope you agree that my case is a question of the DAS signals from the IFZ to the ECU being interrupted intermittently.

I guess i shall be requesting the dealer to release my car ASAP as this is getting nowhere and causing a big hole in my wallet.

*What are the symptoms of a failing wiring harness anyway?