Z4 E85 SRS Error 987B

dmckennitt · 10-08-2023, 08:42 AM

I'm getting a SRS Code - "987B Coding, firing circuit, belt tensioner, rear left, at variance" and trying to locate the failing component. Is this the seat belt tensioner B pillar behind the seat? It appears under the left satellite. I can clear it but reappears immediately once the car is turned off and back on.

Appreciate any thoughts or advice.

Clearancediver · 10-08-2023, 01:59 PM

Are you using a handheld scanner or proper BMW software (ISTAD)…..

If handheld.. suggest you get ISTAD and switchable (pre/post face lift capable) and re-read.

I actually think you are getting an error code for the SRS connector (2 wire) that leads to and is 12-18” approximately from the BST on the battery cable.

This connector is in the battery well on my ‘04 and clipped to the left side of a battery wire connection block.

Why??? Had same issue when an independent diagnosed my fault issue (using handheld) just days after buying car (tensioner). Took it back to dealer who sent me to BMW for corrective action. They correctly diagnosed the issue as that connector… cleaned it up and sent me on my way fault code free. Of course over the next 8 years I had “issues” with that connector and finally cut out and replaced with a non OEM connector of the proper wire gauge. That brough brought the ohm resistance back into spec (1.2-3.4 ohms)

dmckennitt · 10-09-2023, 08:38 AM

Thank you for the response, Yes in this case I used my handheld, I can hook up my computer and run ISTAD... I had already cleaned that connection but like your idea to change the connector. FYI, I did try disconnecting and got a specific code for the circuit being open. Wondering if the variance might be due higher resistance. I will try changing the connector and respond back.

Clearancediver · 10-09-2023, 02:11 PM

Thing with ISTAD is that you can read the actual resistance of that connection….and retest it after cleaning the connection.

Ultimately replacing with a new connector …soldered in and “heat shrinked” with a standard two pin connector vice the “fine” pin OEM connectors had that resistance at 2.2 ohms and no amount of moving the wire was going to cause it to go cause a fault.

10-08-2023, 08:42 AM	#1
dmckennitt Registered 0 Rep 2 Posts Drives: BMW Z4 Join Date: Oct 2023 Location: Cape Cod iTrader: (0)	Z4 E85 SRS Error 987B I'm getting a SRS Code - "987B Coding, firing circuit, belt tensioner, rear left, at variance" and trying to locate the failing component. Is this the seat belt tensioner B pillar behind the seat? It appears under the left satellite. I can clear it but reappears immediately once the car is turned off and back on. Appreciate any thoughts or advice.
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10-08-2023, 01:59 PM	#2
Clearancediver Lieutenant 90 Rep 406 Posts Drives: 2004 Z4 Join Date: Oct 2012 Location: Victoria, BC Canada iTrader: (0)	Are you using a handheld scanner or proper BMW software (ISTAD)….. If handheld.. suggest you get ISTAD and switchable (pre/post face lift capable) and re-read. I actually think you are getting an error code for the SRS connector (2 wire) that leads to and is 12-18” approximately from the BST on the battery cable. This connector is in the battery well on my ‘04 and clipped to the left side of a battery wire connection block. Why??? Had same issue when an independent diagnosed my fault issue (using handheld) just days after buying car (tensioner). Took it back to dealer who sent me to BMW for corrective action. They correctly diagnosed the issue as that connector… cleaned it up and sent me on my way fault code free. Of course over the next 8 years I had “issues” with that connector and finally cut out and replaced with a non OEM connector of the proper wire gauge. That brough brought the ohm resistance back into spec (1.2-3.4 ohms) __________________ Sent from my smart phone...
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10-09-2023, 08:38 AM	#3
dmckennitt Registered 0 Rep 2 Posts Drives: BMW Z4 Join Date: Oct 2023 Location: Cape Cod iTrader: (0)	Thank you for the response, Yes in this case I used my handheld, I can hook up my computer and run ISTAD... I had already cleaned that connection but like your idea to change the connector. FYI, I did try disconnecting and got a specific code for the circuit being open. Wondering if the variance might be due higher resistance. I will try changing the connector and respond back.
	Appreciate 0 Quote

10-09-2023, 02:11 PM	#4
Clearancediver Lieutenant 90 Rep 406 Posts Drives: 2004 Z4 Join Date: Oct 2012 Location: Victoria, BC Canada iTrader: (0)	Thing with ISTAD is that you can read the actual resistance of that connection….and retest it after cleaning the connection. Ultimately replacing with a new connector …soldered in and “heat shrinked” with a standard two pin connector vice the “fine” pin OEM connectors had that resistance at 2.2 ohms and no amount of moving the wire was going to cause it to go cause a fault. __________________ Sent from my smart phone...
	Appreciate 0 Quote