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Rover 75 2.0 Diesel 2002. Airbag pretensioner fault

Posted By jonastra1 Thursday, June 14, 2012 8:39:03 AM
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jonastra1
 Posted Thursday, June 14, 2012 8:39:03 AM
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I have a Rover 75 with me at the moment and it's kind of stumped me. The airbag system has 2 fault codes stored suggesting a high resistance in both the front and the rear driver's side pretensioners. I have fixed the rear one, caused by a high resistance in one of the firing circuit wires. But the front one is strange. The front pretensioners are wired in series on this car, so if the firing circuit is open circuit to on side, both pretensioners show up as faulty. So how then can the module bring up a high resistance to only one of the pretensioners?

Fault code 0806 right front pretensioner high resistance.

All advice appreciated.
sparki1
 Posted Thursday, June 14, 2012 1:22:22 PM
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What are you reading it with, I have seen this using a DEC on some renaults, the description says front left. but in reality because they are in series it cant know which it is. Dummy loads and live data is the quick way forward I suspectSmile
jonastra1
 Posted Thursday, June 14, 2012 1:29:03 PM
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Yes i should have said i fitted 2 dummy squibs and measured the resistance in the front circuit and it seems ok. losing the will to live.
lukiep
 Posted Thursday, June 14, 2012 2:00:30 PM
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Hi, when i worked for rover we used to see no end to these throwing srs lights on, most of the time it was a case of removing the connectors and soldering the wire together. Also there will be another connector under the seat for the side bag make sure you get the right one.

Chevrolet Tech
Tismot
 Posted Thursday, June 14, 2012 3:32:46 PM
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>>> how then can the module bring up a high resistance to only one of the pretensioners? <<<


By spitting the circuit ( a reference wire fitted between the two consumers) and monitoring the "split" values the ECU could work out the resistance of each one.

Get a proper wiring diagram and if possibile get the vehicle on T4

Mark


Modern cars, Its all wizardry and witchcraft
Thursday, June 14, 2012 3:34:30 PM by Tismot
jonastra1
 Posted Saturday, June 16, 2012 8:45:56 AM
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Thanks Tismot and other replies, I'm using the dealer wiring diagram and i have more than 1 proffessional scan tool.

It is simply wired 1 wire to each pretensioner and 1 wire that only runs between the 2 pretensioners, never going near the ecu.
jonastra1
 Posted Saturday, June 16, 2012 2:37:57 PM
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Ok this is fixed now.

Problem was staring me in the face. On dealer wiring diagram Pins 22 and 23 form the loop between the 2 front seatbelt tensioners. Pins 24 and 25 go to rear centre pretensioner. These wire designations are correct in accordance with the manufacturer's diagram.

Autodata gave me another (older) wiring diagram. It details left front pretensioner on a separate 2 wire circuit (pins 22 and 23.) Right front pretensioner which is also 2 wire works off (pins 24 and 25.)

So i added a squib to pins 24 and 25 (rear centre pretensioner circuit) and the light went out!

I have concluded that at some time in this vehicle's life it has had a Airbag ecu fitted to it from an older car.
Now i will have to locate a airbag module from another car as this srs set-up is not safe.

Thanks for the help.
Saturday, June 16, 2012 2:39:47 PM by jonastra1
K And R
 Posted Saturday, June 16, 2012 5:08:17 PM
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Jon.

Perhaps you can answer a question asked earlier What scanner ?

"have concluded that at some time in this vehicle's life it has had a Airbag ecu fitted to it from an older car."

because it has basically broke into a wrong ecu.

My data shows for a 2002 75 as rear centre pre-tensioner as pin 49 and 50. Is this a low line ?

Kev.


"If you dont KNOW how it works, don,t try to test or fix it"
jonastra1
 Posted Monday, June 18, 2012 8:43:54 AM
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Kev,

Thank you for the interest. On this vehicle i have pretty good coverage on my Autodiagnos Scanner. (maybe not on some other makes!) I've had Autodiagnos since year 2000 and it owes me nothing at this stage. Great tool until Crypton swallowed it up and then spat it out to omitec.

The wiring diagram you have is for the up to 02 rover 75 and that is indeed the correct pin designation for that component on that ecu.
If you look at pins 24 and 25 however, on the system i have, those wires go to the centre rear pretensioner on this car.

If this car was involved in an accicdent, and by some fluke the car had accepted the squib resistance values, the crash sensors are wired to the driver's airbag circuit, so if a crash was sensed it would not have deployed the nescessary airbags but instead would have shown up as a fauly drivers airbag circuit. the right rear pretensioner is wired to the drivers head airbag, the drivers airbag would have blown out if the drivers side airbag command was given etc etc

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