L322 Restraint Control Module Not Recognised

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C1PLR

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Cheltenham
Hello All,
I have my airbag light on consequently can not pass my MOT :-(
I have attempted to reprogram the existing module in SDD but this always fails, I have now replaced the module with a second hand one which was not recognised....but not the original failing one is not recognised either. So I am not sure if the original one was faulty in the first place or something else may have been causing the problem....anyone got any pointers please?
 
Not related to the RCM, it just can't be seen:
 

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I know very little about the can-hs bus but it doesn't seem right that it can't see any of them modules, IMO you have something dragging down the whole bus.
 
I am not sure if I am looking in the right place for this issue. I built a clean VM, reinstalled the software and was able to see all the modules, until I disconnected the RCM and tried to connect the new one... now back to the same problem.....
 
C1PLR said:
Hello All,
I have my airbag light on consequently can not pass my MOT :-(
I have attempted to reprogram the existing module in SDD but this always fails, I have now replaced the module with a second hand one which was not recognised....but not the original failing one is not recognised either. So I am not sure if the original one was faulty in the first place or something else may have been causing the problem....anyone got any pointers please?
Click to expand...
Whats the last 8 of chassis number
 
If only the rcm is offline its not a can network fault depending on what year vehicle is if its k bus or can network. Can high should get a reading of 2.7 and can low 2.3 the only wiring you need to test if a module is not responding is. power reading should be battery voltage +or- 0.5v easiest way to check earth is meausure voltage at earth wire at module if above 1.0v earth needs to be checked if you let me know what year vehicle is i will let you know wiring colours and pin locations
 
Can high and low are always on separate pins. Basic measurements can be taken with a multimeter basically both voltages added together should add to 5 volts. pico scope is the best way to diagnose can issues as when a can trace is viewed at 20 miliseconds the pulses of 0 1 code can be seen
 
Having googled it I agree about the two pins and now know why it's done that way but given that they are high speed pulses I wouldn't have thought a multimeter will work.
 
Ye multimeter will work if you get 2.7v on can high and 2.3 v on can low can system should be communicating as long as module has power earth and can it should be online. The other way to test a can network is disconect battery and measure resistance at obd port can network should have resistance of 120ohms as all can network have 2 terminating resistors each measuring 60 ohms
 
I have wiring/network dias for a 2011 but not sure if they would be the same as by the looks you are 2007.

@C1PLR
 
Miloman59 said:
Ye multimeter will work if you get 2.7v on can high and 2.3 v on can low can system should be communicating as long as module has power earth and can it should be online. The other way to test a can network is disconect battery and measure resistance at obd port can network should have resistance of 120ohms as all can network have 2 terminating resistors each measuring 60 ohms
Click to expand...

Ok just watched a very interesting youtube tutorial (it was American but still). The modules on the CAN HS transmits data strings of 0's & 1's at upto 1MBS so I don't see how a multimeter can measure that in any meaningful way, I still think it needs a scope to see if the data bits are valid or just noise, i.e all 0's or all 1's or even 0v or 5v if seriously screwed.

Also from what I remember 2 x 60ohm resistors in parallel give you 30ohms. The youtube video has 120ohm terminating resistors which IMO gives you 60ohms.

Interesting stuff to me but probably putting some to sleep :D
 
Alternative to PicoScope is the Hantek 1008C for a fraction of the price. The cost varies a bit depending on how many probes to require. The software wants Windoze, but also works ok using a VM on Macbook. It will show the CAN databus is working but doesn't decode the data.

I used mine to diagnose a misfire using Cam & Crank sensors, plus spark probe to check each HT lead in turn . . . .really easy.
 
pwood999 said:
Alternative to PicoScope is the Hantek 1008C for a fraction of the price. The cost varies a bit depending on how many probes to require. The software wants Windoze, but also works ok using a VM on Macbook. It will show the CAN databus is working but doesn't decode the data.

I used mine to diagnose a misfire using Cam & Crank sensors, plus spark probe to check each HT lead in turn . . . .really easy.
Click to expand...

I've used mine to test my FBH, amp output when I had a melted speaker, and height sensors. Mine came with all 8 probes. As you say for the price it was a no brainer.
 
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