BMW Positive Terminal Battery Cable Repair Kit How to Fix It Cheaply

Difficulty starting the vehicle after an accident is one of the first symptoms of a problem with the battery terminals or loss of electrical power. This usually occurs when a vehicle has faced an accident and resultantly the battery positive terminal explodes to prevent the car from further damage. The actual reason for this problem is the BMW battery safety terminal (BST) sensor fault, which is mounted on the positive terminal (also known as the pyroswitch/pyrofuse) as part of the battery positive clamp that attaches to the battery post and in an event of accident; BST triggers and disconnects the B+ cable going to the starter and alternator.

Battery safety terminal as the name implies, is designed to disconnect the battery when the car is involved in an accident. It performs a vital function for the overall functionality and safety of the BMW battery. When BST sensor fails, it triggers the airbag light to come ON. Once the BST is ignited it may not be reused and needs to be replaced.

In this guide, we will see how to install a BMW battery safety terminal kit and reset BMW air bag light which comes ON when the BST sensor fails.

How do we know that BST failed?

If you are unable to start your BMW, make sure that you checked the positive cable of battery is not loose. If you find it loosed, it means that BST ignited and disconnected the positive terminal which is hampering the ignition of your BMW.

Symptoms of bad or failed BST include:

Your BMW is not starting after an accident
If airbags deployed BMW will not start
BMW doesn’t start but accessories and light works
Airbag light is ON

How to fix bad BMW battery safety terminal

The only solution for a bad BST is the replacement. You can either buy a new clamp (bmw Auto Cable Masevaux) battery terminal cable with pyroswitch which is a bit costly option or just replace pyrofuse which is a cost effective option and save you a lot of money. Also, the replacement can be done by yourself or you can take it to the professional mechanic to perform this replacement.

How to install BMW positive battery safety terminal kit

Replacement of BMW BST is not time consuming but it can be tricky as it is all about the electrical connections your vehicle has with the battery.

Very minimal and basic apparatus is required to replace BMW battery safety terminal which includes.

BMW BST cable pyroswitch
10mm open-end wrench
Flat screwdriver

Replacement method

First of all, park your BMW in the leveled ground, turn off the ignition and engage the parking brakes.
Open the trunk and release the plastic retainers from the right side to access the battery safety terminal
Use a 10mm wrench to disconnect negative and positive battery terminals in order
Before removing BST /fused pyroswitch, unplug the two black wires which are for the airbag. Then, remove the nut connecting accessory cable to the battery clamp.
Install a new pyrofuse and reconnect the black wires for airbag module.
Connect positive terminal first and then negative battery terminal
Locate the diagnostic port and connect the scanner that can read airbag fault codes such as FoxwellNT510 for BMW. Keep in mind that a basic code reader won’t clear airbag faults codes. Clear any BMW fault codes stored in airbag module

If the BST is exploded, it should be replaced. But many BMW owners decide to bypass the BST sensor which is not recommended.

Bypassing BST sensor

Battery safety sensor can be bypassed by cutting the wires to the sensor and installing a resistor. Doing this will clear the airbag light but a key safety feature will be disabled and the chances of fire damage are increased if your car meets an accident.

Some BMW owners would bypass the BST sensor and connect the positive cable directly to the battery positive terminal because of the hefty cost they were required to pay for the BMW battery safety terminal but today you can get a BMW BST repair kit for a fraction of original prices. This repair kit also kills the needs to buy brand new expensive whole clamp battery cable (plus pole) and saves your money. Usually, coding is not required after replacing positive battery terminal cable end's pyroswitch.

Below you'll find some bmw oem part numbers.

BMW battery cable (plus pole) part numbers:

61126821904 61129322056
61126989780 61129217017
61129225099 61129217033
61129253111 61129322056
61129259425 61126834543
61129217004 61129217036
61139203570-04 61129217031
61126988974 9217036-02
9184191-01 7792130
9259425-02 6929324
618537-101 9350065-03
9391187-01 618540
61129391187 61128704706
6988972 6988974-01
10304410 9217004-01
9350064 65508757
618540-101 9391187-02
6112704746 61126938495
6989779 6989780-03
9127768 6989782-02
9217030 9217031-01
9259424 9253111-03 6989780-02
9217033-02 9217032
9217033-01 9217036-01
9232586 9217034 9217035-01
9232587-02 6944536
9321004 2557087-01
2557087-01 61129321005
6834543-02 6835243
9259425-03 9217018-01
65275149 65169877 618537-103
9115449 9115438
61128796155 61128796959
9322056-03 9322055 9367471
61129127780 9127780
9127036-01 6989784 9127780-01
8704706-01 8704745
61129359665 8801729 2557834
2557835-02 8801729-01 619919-107
65428083 65346373 61128796040
8796042-01 61128795489 61128796048
61128795485 8795485-08 61128796044

BMW B+ junction point, rear fuse box:

6802944-02
61146802944
61149339832
933983205

BMW battery cable (plus pole) part numbers:

BMW B+ junction point, rear fuse box:

6802944-02
61146802944
61149339832
933983205