ABS Terminating resistor / CANBUS issue

[frmtaat]

Hello everyone,

This is going to be my first post here, so let me start with a huge thanks to everyone who ever contributed to this forum, i have spent many-many hours browsing the topics and learned so much here. Thank you! I was born and raised in Hungary, Europe, English is not my native language so please forgive me whenever my spellig is incorrect or i sound silly....

Now with actual issue in subject:

I have an issue with my CANBUS system. About every two to theree days my DIM says "BRAKE FAILURE STOP SAFETY ASAP", and looses communication with all high speed modules, idle becomes erratic just like if i would pulsing the accelerator pedal, loose speedo and rpm meter. If i turn off the engine, it refuses to start (it cranks but wont start). If i hook it on VIDA, it can not communicate with any of the modules (ABS, ETM, ECU, ECM).

I had the usual issues/sings of a failing ABS module for a couple of month now (ocassionally loosed speedo, brake failure message etc.) but never the complete failure symptoms of the CAN network.

If unhook the battery and leave it for like 5 minutes it fires up perfectly like no issues. This works all the time.

I suspect that my failing ABS module is giving false signals to the CAN wires forcing the CAN network go crazy hence i need to reset the computer to work again.

I would like to remove the ABS module and test if the culprit is the ABS however VIDA says that the terminating resistor is built in to the control modules, so if i just remove the ABS it would levave me an unresisted loop/end in the CAN communication, which could cause the same issues as a faulty unit...Is this valid or am i wrong?

Do you have any further ideas regardig this issue?

Many thanks in advance,

Mate (thats my actual name )

(EDIT: Car is 99' S80 2.4i, manual, naturally aspired, ABS without STC or DSTC.)

[RickHaleParker]

CAN BUS termination is 120 Ω at each end of the bus, for a combined resistance of 60 Ω.

[frmtaat]

Thanks Rick!

Yes, CAN l and CAN H should have a combined resistance of 60 Ohm. Vida says that there is a built-in terminating resistor of 120 ohms in both ends of the network (one in the ETM and one in the ABS moudle) which bridge CAN H and CAN L to prevent electrical reflections and interference.

So, if i just simply unplug the ABS module leaving one end of the network without a terminating resistor can cause interference in the CANBUS communication and result in such a scenario discribed above? (communication go crazy, offline modules, no start etc...)?

If yes, can i just simply put a 120 Ohm resistor in between the ABS plug's CAN H and CAN L pins to mitigate this issue? Or it's not that simple...?!

I think that the cranking but no start might be because even if the starting operation is allowed by the CEM, the OK singnal is unable to be received by the ECM due to "blocked" network? But these are just my -not so- educated guesses...

[RickHaleParker]

If yes, can i just simply put a 120 Ohm resistor in between the ABS plug's CAN H and CAN L pins to mitigate this issue? Or it's not that simple...?!

High and low speed sectors

The network consists of two sectors with different transfer rates.

The engine compartment sector, which requires fast communication, has a transfer rate of 250 kbps.
The passenger compartment sector, which does not require such fast communication, has a transfer rate of 125 kbps.

The connection of these two sectors is provided by the Central Electronic Module which converts the communication between the network sectors up or down.

High speed only in the engine compartment. One of the wires is a ground.
The CANBUS is pins 11 & 12. That is where the CANBUS Terminates.

[frmtaat]

My issue is gone once i put a 120 ohm resistor between ABS connector pin 10 and 11 (CAN H and L wires), no more crazy signals and communicaion loss while ABS modul is not in the car. Unfortunately my intermittent no start issue is still on so it seems like unrelated to the faulty ABS module. Thanks for all your inputs.

[RickHaleParker]

If unhook the battery and leave it for like 5 minutes it fires up perfectly like no issues. This works all the time.

Unfortunately my intermittent no start issue is still on so it seems like unrelated to the faulty ABS module. Thanks for all your inputs.

Are you leaving the key in POS II when you reconnect the battery?

If so: Next time it will not start.

• 1. Turn key to POS 0.
  2. Turn key to POS II.
  3. Wait 15 seconds.
  4. Crank engine.

Your fuel pressure might be bleeding off as it sits. Waiting 15 seconds gives it time to build back up.

[frmtaat]

Thanks Rick. Yes, key POSII and headlights on every time...Thanks for you tip, but it seems like i have an issue with ECU. I been finally able to hook it on vida while showing the non-start syptoms (i never had my laptop and dice with me when it won't start and removing the battery was cleared all my codes...

So the codes were the following:

ECM003 Configuration fault, which is generated generated if the engine control module (ECM) registers that the software does not correspond with the other vehicle configurations. This is strange as no hardware on CAN HS were replaced on the car and no software updated were made, for sure not in the past couple of years.

ECM-902B Communication with throttle unit. Signal too low. Vida says If the engine control module (ECM) has not received a system relay deactivation request from the electronic throttle module (ETM) within 10 seconds of the ignition being switched off the code is set. This is interesting, as i noticed one or two times that my ETM was not stopped the whinning noise after the ususal 6 seconds after ignition on (but engine not started) but keep that high pitch sound until i turned off the ignition. Related?! Or maybe code just set since ETM is after the ECM so faulty communication with ECM can bring various ETM DTC's?!

ECM-720A Immobilizer communication. Faulty communication. I believe that this is only because the faulty communication b/w CEM and ECM, i have checked the CEM immo stats in vida and all seems ok (start possible, main key, yes TP response, TP status OK, CEM-ECM start signal positive HOWEVER CEM-ECM data received: NO and hence no frequency input form ECM to keep fuel pump alive. So i think it is because faulty CAN communication but immobilizer function works OK.

CEM-E000 Control module communication. Faulty communication. Fault set if the control module registers serious interference on the high speed network (CAN communication blocked). That make sense, but what causing the serious interference?

I have tested the CAN wires many times, 60+-1 ohm always. I have the ABS modul removed but a 120ohm resistor is placed between CAN H and CAN L pins. I am still unsure if the removed ABS module can cause such a communication fault? It would be so hard to believe...

Do you have any idea which could steer me to the right direction? I would order a rebuild ECM and ABS 100 times by now from XemodeX, but with shipping and VAT and custom tax to Hungary Europe it would be a nightmare and no such a trustworty company can be found anywhere nearby in Eastern Europe...

Thanks as always!

[RickHaleParker]

Typo error in the first code. missing a digit.

Did you clean the connectors on the ECM and CEM. A little oxidation on the connectors can wreak havoc on CAN BUS communication.

Do you have any idea which could steer me to the right direction? I would order a rebuild ECM and ABS 100 times by now from XemodeX, but with shipping and VAT and custom tax to Hungary Europe it would be a nightmare and no such a trustworty company can be found anywhere nearby in Eastern Europe...

MVS member Yagger has a commercial business that does Volvo programing over the internet. If it turns out to be a defective control module, you can acquire a use one in Hungry then hire him to reprogram it over the internet.

Yagger's website: ONLINE SERVICE (for Volvo only)

You might need to build a CEM pin cracker or buy the one Yagger has. Currently Yagger's PIN cracker will get him the PIN and it is not shared with the customer. All the online programing services do not share the PIN number with the end user. However if you acquire the CEM PIN on your own, they will put it to use.

[yagger]

I think you have to focus on CEM also.

[RickHaleParker]

A defective control module on the CAN Bus can trip all the codes you have listed.

CEM-E000 is tripped by a serious interference on the high speed network.

CEM-E000 takes the CEM off the CAN BUS. Preventing communication with the other control modules. The CEM will remain offline until the power supply is broken (15, 30, X). When the power supply is reconnected the CEM will make a new attempt to communicate. You first goal is to get the CEM back online and find the source of interference.

CEM-E000 Possible source

• Short-circuit between the control area network (CAN) wiring
  Open-circuit in the control area network (CAN) wiring
  Internal fault in the control module
  Internal fault in another control module in the same part of the control area network (CAN).

Have you tried clearing the codes with the ABC disconnected and the CAN BUS terminated with a 120Ω?

Clear the codes with the ABS disconnected, Key off, disconnect and reconnect battery and see if the codes go away and stay away. List any codes that do come back. Do not reconnect the ABS, clearly it is causing serious interference.


Note: Battery disconnect and reconnect procedures
1. Key off.
2. Disconnect negative battery cable.
3. Wait 30 seconds or more.
4. Key in POSII
5. Reconnect negative battery cable.
This forces the control modules to reinitialize.