Airbag fault code 1738

[Loren]

Fault code 1738 Airbag sensor (driver's) - Fault code 1739 Airbag sensor (passenger's)

 

Possible cause of fault
♦ Implausible signal (incorrect airbag sensor installed)
♦ Open circuit (based on wiring between airbag triggering unit and airbag sensor or the airbag sensor itself)
♦ Electrical fault in electric circuit (based on wiring between airbag triggering unit and airbag sensor; probably a short circuit to B+ or a short circuit to ground)
♦ Faulty (airbag sensor is faulty)
♦ Airbag triggering unit faulty

[Anderson]

If this is your problem: Electrical fault in electric circuit (based on wiring between airbag triggering unit and airbag sensor; probably a short circuit to B+ or a short circuit to ground)

(2137-Battery Disconnection relay) on my diagnostic tool Icarsoft Por V2.0) 

I had this problem on my Cayenne S 2005 some months a go. I needed the airbag light to go away before sending the car for inspection, MOT in UK, and car Besiktning here in Sweeden. I literally checked all my airbag connections, wiring and looked for corrosion on the chassis. It took me quite a lot of time and as a result I found nothing out of the ordinary.

I visited every forum  on the web related to Airbag faults but couldn’t find a single post that would help me locate where the short could possibly be coming  from. 
Then I decided to Ieave my car at Porsche Gothenburg for diagnostic. They worked on my car for two hours and told me that the airbag relay sensor needed to be replaced and they wanted to order one for my car, but they weren’t sure if it would solve the problem once replaced… I decided to bring the car back home and experiment myself instead of paying the dealer to do it and expend a lot of money without been certain that the problem would be solved.

I went on ebay and got myself a secondhand one and replaced it. Nothing changed, even replaced all relays on B+ circuit just to be sure, nothing… so the problem wasn’t the relay itself (the magical moment when you loose hope and are almost giving it all up) So I decided to wrap it up for the day and probably forever lol, that’s when I paid attention to a no airbag related issue-thread that I overlooked while doing my  search . The thread talked about the B+ circuit and it’s wiring and how dull it was that all Porsche Cayenne’s cables passes under the drivers seat in order to reach the fuse panel under the  hood, and how it frequently causes short circuits due to cable corrosion. That’s right, the water from our shoes during rainy or snowy days can get to the cables and after some years, it turns the affected wires literally in to dust.

Eureka! Bingo! 
So I rushed and lifted the carpet under the drivers seat and under the pedals… didn’t take long to see a broken black wire flying around… I followed the wire and realized that the black wire’s other half was connected to the airbag relay sensor’s conector, so I soldered the wire back together and when I reconnected the battery , the dash’s airbag warning light was gone! 
 

Hope it helps!

 

Here we have some pictures to better understand what we have discussed:

Porsche Cayenne S 2005 Airbag light issue. - Google Drive

DRIVE.GOOGLE.COM

 

Edited August 15, 2021 by Anderson

[Werner R]

On 8/13/2021 at 2:22 AM, Hughandjen said:

Hi folks 

I have a 2003 955 4.5s. I have fault codes 1738 and 1739 airbag sensor faults. I have replaced both the front sensors under the headlights to no effect. I have soldered the joint wires under the seats to no effect. My icarsoft por 2 reader give these faults; 

Resistance- battery open circuit 

seat Occupancy passenger too big and

Resistance- driver side airbag too small

i see that many people have had these faults but there doesn’t seem to be an answer?

any help folks!!!

 

Hello, I have almost the same problem as reported by Hugh(andjen). The airbag light on my 2004 Cayenne S would come on intermittently and after a few weeks like this it has become permanently on. My iCarsoft CR V3.0 shows fault codes 1738 and 1739 which cannot be cleared. The solder connection under the seat is already done. This weekend I will lift up the carpet on the driver side to inspect the cables. It is odd that both 1738 and 1739 are shown at the same time and one would think that it is unlikely the cables under the carpet on the passenger and driver side became defective at the same time but I am grasping for straws at this time.

 

Has anybody another idea what else I should be looking for?

 

Thanks.

 

Werner

[Josh R D]

Good Hey guys Josh from Australia, i brought a 2005 cayenne s few months ago with light all over the dashboard and managed to decipher then all to fix all the problems. Originally i had a blown fuse plus the standard corroded wiring on the Left front side in the cab, once i fixed that all up i had no drama for abit then i got code "2137 open circuit in battery (electro-Mechanical)" with to high of a resistance in battery circuit and passanger seat occupancy sensor. if i disconnect the occupancy sensor i get a code for passeneger seat air bag resistance. Im a mechanic by trade with my own business that uses a SnapOn Trition D10 scan tool. Just wondering if any one has some pointers or a Circuit Diagram of the SRS system so i can pinpoint a shorted wire

[Loren]

3 hours ago, Josh R D said:

Good Hey guys Josh from Australia, i brought a 2005 cayenne s few months ago with light all over the dashboard and managed to decipher then all to fix all the problems. Originally i had a blown fuse plus the standard corroded wiring on the Left front side in the cab, once i fixed that all up i had no drama for abit then i got code "2137 open circuit in battery (electro-Mechanical)" with to high of a resistance in battery circuit and passanger seat occupancy sensor. if i disconnect the occupancy sensor i get a code for passeneger seat air bag resistance. Im a mechanic by trade with my own business that uses a SnapOn Trition D10 scan tool. Just wondering if any one has some pointers or a Circuit Diagram of the SRS system so i can pinpoint a shorted wire

 

Fault code 2137
Open circuit in battery (electro-mechanical)

Diagnostic conditions
• Ignition on
• Internal function test on airbag triggering unit

 

Possible cause of fault
• Short circuit to B+/ground/between wires or open circuit in wiring to cutoff relay
• Cutoff relay faulty
• Triggering unit for airbag faulty

Affected pins
Airbag triggering unit: Pin 4
Airbag triggering unit: Pin 76

[Josh R D]

thanks loren for the info much appreciated!!!