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   #21  

Jef

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2009 S5, MMI not working, no communication with anything on the infotainment bus. As per par for the course "we've checked everything"....

I ask the tech to go to [Applications] - [Optical Bus Diagnostics] then [Start]. Gets electrical error for the Control Head which is the J794 on this car. Check fuse ST3 SF5.... and there is no fuse.

Pops in a fuse....



MMI working now. Need to file a police report, the fuse bandit has struck again!
 
   #22  

Jef

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2009 A4... 43 fault codes in the engine. Tech cleared them out and tried to test drive, can runs very poorly and 43 fault codes again. Starts rambling off generic key works in the fault codes.. engine mounts, EVAP, intake runner, cam shaft..

OK, lets stop there... the cam shaft one, what is the P code? P11A1 Cam Adjustment Actuator A; Cylinder 1 open circuit... lets just worry about that one fault code... this goes back to fuse SB7, is that fuse good?

Does some digging to access fuse and it is popped.



Codes clear out now... will do follow up test drive.

Tech was overwhelmed by the number of fault codes. If you got a crazy shopping list and see a common theme (open/short codes in this case), then pick just 1 item and worry about it. In many cases, similar failures are related so fixing 1 simple issue fixes 42 other issues.
 
   #23  

Jef

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2019 Atlas, some front end damage due to whatever... but now the ECM is loaded with fault codes.

  • 24989 - Control Circuit for Coolant Bypass Valve P2682 00 [039] - Short to GND
  • 12347 - Coolant Pump Control Circuit P2602 00 [039] - Short to Ground
  • 9042 - Bank 1 Camshaft B (Exhaust) Position Actuator P2090 00 [101] - Short to Ground
  • 11942 - EVAP System Leak Detection Pump Heater Control Circuit P240B 00 [039] - Short to GND
  • 11939 - Control Circuit for EVAP Vent Control P0448 00 [039] - Shorted
  • 11948 - EVAP Leak Detection Pump Control Circuit P2401 00 [039] - Short to GND
  • 2798 - Bank 1 Camshaft A (Intake) Position Actuator P2088 00 [101] - Short to Ground
  • 9028 - Intake Manifold Tuning Valve Control Circuit (Bank 1) P0661 00 [101] - Short to GND
  • 4235 - Evap System Purge Control Valve (N80) P0458 00 [039] - Short to Ground

.... So again, pick an easy item, Bank 1 Camshaft B (Exhaust) Position Actuator in this case... this is the N318 Exhaust Camshaft Adjustment Valve 1 in the factory wiring diagram... start tracing it back... and we land on fuse SB4. So how is fuse SB4?



Replace fuse, car is happy.

The guy here at the body shop told me he checked fuses.
:facepalm:
 
   #24  

Jef

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2010 Tiguan, for whatever reason the subframe and power steering rack (J500) was removed. Everything put back together and now there is no power steering, no comm with J500. Made sure the J500 was plugged up. OK, so get an old school incandescent test light, ground the clip on the battery and check fuse SA2....

 
   #25  

Jef

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2017 Passat at a body shop.. .uh oh... light front end damage and has been repaired. A mobile tech, Kirk, is being told by body shop that customer stated there were no issues with the car prior to the fender bender. The ABS and CAN Gateway have this code:

02849 - Control Module for Lane Change Assistance (J769)
004 - No Signal/Communication

Looking into the wiring diagrams... there ain't much info about the J769 other than it is located at the right rear of the car, and it is wired up on the CAN BUS network (duh)... but I can't find any more info. Kirk needed to head out, I'll do more digging and call back with what I learn.

I do find info on the J1086 which is listed as the Blind spot detection control module, located in the right rear. I'm not sure, but I think it works like this:

  • Fully loaded car, you get a J769 - Lane change assistance control module (with ACC)
  • Base model car, you get a J1086 - Blind spot detection control module (without ACC)
Back in touch with Kirk, explain the J769 vs J1086 but at any rate, check out fuse SC17, that is what powers the J1086. He will relay the info back to the body shop.

Kirk calls back, body shop claims they fixed everything and the only issue was the LED light for blind spot warning on the right side view mirror was not plugged up. I call BS, there is no way having a LED ligth unplugged caused a module to be off line. Kirk agrees, this story doesn't pass the sniff test and he will try to get back to the car.

Back at the car, Kirk finds that nothing is fixed, still no comm codes in ABS and CAN modules. Take a look at fuse SC17....



Replaced missing fuse, all codes clear out, car is happy now.
 
   #26  

Jef

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2012 Jetta, clock spring was replaced and now it has codes for no comm with Steering Angle Sensor (G85). Tech was thinking the car needed the Steering Wheel Electronics (J527) code. Submits an Auto-Scan:

01-Engine -- Status: Malfunction 0010
02-Auto Trans -- Status: Malfunction 0010
03-ABS Brakes -- Status: Malfunction 0010
04-Steering Angle -- Status: Cannot be reached 1100
08-Auto HVAC -- Status: OK 0000
09-Cent. Elect. -- Status: Malfunction 0010
15-Airbags -- Status: Malfunction 0010
17-Instruments -- Status: OK 0000
19-CAN Gateway -- Status: Malfunction 0010
25-Immobilizer -- Status: OK 0000
56-Radio -- Status: OK 0000
Eh, this car is poverty spec (PR-AW0 Low Line), a quick look at the wiring, G85 is powered by fuse SC27, a big phaaat 1A fuse.... tech starts looking under dash...



There is no fuse in SC27. Replaced missing fuse, G85 back online.
 
   #27  

Jef

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2011 Jetta, engine doesn't crank.

Car at repair shop. Owner tells tech this happened after he (owner of car) pulled the radio out. I'm told there are no fault codes anywhere, and the instrument cluster always has a message to push clutch pedal in to start, even if clutch pedal is on the floor.

This car uses a Clutch Position Sensor (G476). Gets power from fuse SB10 as per wiring diagram... so how is fuse SB10? Tech pokes around for a minute... good. OK, G476 at T5m/5 do you have power? Nope. SB10 is good? Double checks... well, all fuses here are good... oh, position 10 is empty.



Popped in a fuse, car cranks overs over and fires up. Asked tech to touch base with owner of vehicle... fuse ≠ radio
 
   #28  

Jef

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2012 Passat, AC doesn't work. Customer brings car to shop wanting AC compressor, condenser and dryer. Tech blindly does this as per customers request. All back together, AC doesn't work. Are there any fault codes in the HVAC control module? Yes, one:
  • B10AE High Pressure Sensor short to ground
Did it originally have this fault code? Yes, pretty sure it was there to begin with. The AC pressure switch, G65, do you power and ground across /1 and /3? No power. OK, take a look at fuse SC4, it is good? Tech pokes around for a minute... it would seem the fuse was visited by a fluffer at some point.

Replaced blown fuse, AC now works.
 
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