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G.M. Vehicles With Loop Resistance Problems
Posted to Technical Tips Forum on 4/7/2016 87 Replies

Most late model G.M. vehicles have inflatable restraint loop resistances that can be accessed through a scanner. This greatly facilitates diagnosis/repairs. Today, I worked on a 2016 Chevrolet Equinox with 6 miles that had a SIR lamp and service warning on during PDI.

Step 1 ... What code is set?


OK - B001A-0E - driver's side seat belt anchor pre-tensioner loop resistance low.

Step 2 - Check resistance of pre-tensioner loops. I selected loops 1 -14 to check with GDS2.

[Resistance Readings]

All loops have about 2.5 ohms resistance except for loop 7 which is low at .4 ohm. The problem could be anywhere from the SDM to the anchor pre-tensioner or associated wiring harnesses.

Step 3 - Check for a grounded harness under the seat. I graphed the resistance while gently moving and wiggling the harness under the seat.

[Resistance Loop 7]

No change noted there. We can start testing from either end of the circuit, but, since I'm already under the seat, let's just unplug the anchor pre-tensioner first.

Step 4 - unplug pre-tensioner

[Unplugging Pre-tensioner]

Well, that's pretty obvious isn't it? The tensioner is internally shorted. Time to replace the anchor and retest.

Step 5 - Confirm Repair

[New Pre-tensioner]

Loop 7 is now in the normal range and the service light is off. Just need to clear the code and ship it. A lot easier than plugging in resistors or simulators, isn't it?

James from Florida

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