help ecu problems maybe????
Thread Starter
AudiWorld Newcomer
Joined: Dec 2017
Posts: 4
Likes: 0
help ecu problems maybe????
Ok im in a jam. So I was driving along fine and dandy. Then boom car suddenly dies, no sputter no check engine no nothing. Got a tow home, Started checking power to the fuses. No power to fuel pump. No power to any of the engine timing fuses. power to all other fuses. Fuel pump relay in engine bay is clicking when i turn the key on. also when i turn the key to the on position i have no check engine light on. all other lights come on including the one with the car and key( immobilizer i think ) and when i turn the engine over i get nothing on the Tach. so i changed the crankshaft position sensor think that was the problem but still didnt fix. tried hooking up vag com and it wont connect. neither will obd which it used to but not now. so how do i go about checking the ecu. or maybe reset the immobilizer maybe. but dont understand why the immobilizer would cause me to not be able to communicate with the ecu... any ideas would be greatly appreciated.
AudiWorld Member
Joined: Jul 2017
Posts: 128
Likes: 7
I recently had a problem not being able to communicate with OBD, if you have a volt meter you can do a quick check. Google "OBD pinout" to get the pin orientation. Pin 1 should be switched battery voltage, i.e. when the ignition is off it is zero volts relative to ground and when the key is on it should read between 12 and 13 volts. Pin 16 is battery voltage regardless of the key position. Pins 4 and 5 are "chassis ground" and "signal ground" which would indicate they are different, but in the Audi the 2 wires are tied together so you should have a solid ground on those 2 pins. If those four pins all check out OK then you have a bad "K line", the OBD signal on pin 7.
The K line is linked to all the control modules and a problem with any of them can mess up the signal. I plugged in my OBD reader and watched it while unplugging control modules. I have read here on the forum the ABS module is often the culprit but in my case it was the headlight leveling control module. As soon as I unplugged it I was able to communicate. I would love to know the decision process that led Audi engineers to put a control module on the floor of the well under the convertible top, one place in the car you can be sure will get wet.
The K line is linked to all the control modules and a problem with any of them can mess up the signal. I plugged in my OBD reader and watched it while unplugging control modules. I have read here on the forum the ABS module is often the culprit but in my case it was the headlight leveling control module. As soon as I unplugged it I was able to communicate. I would love to know the decision process that led Audi engineers to put a control module on the floor of the well under the convertible top, one place in the car you can be sure will get wet.
AudiWorld Newcomer
Joined: Jun 2021
Posts: 1
Likes: 0
Same issue I’m having
Ok im in a jam. So I was driving along fine and dandy. Then boom car suddenly dies, no sputter no check engine no nothing. Got a tow home, Started checking power to the fuses. No power to fuel pump. No power to any of the engine timing fuses. power to all other fuses. Fuel pump relay in engine bay is clicking when i turn the key on. also when i turn the key to the on position i have no check engine light on. all other lights come on including the one with the car and key( immobilizer i think ) and when i turn the engine over i get nothing on the Tach. so i changed the crankshaft position sensor think that was the problem but still didnt fix. tried hooking up vag com and it wont connect. neither will obd which it used to but not now. so how do i go about checking the ecu. or maybe reset the immobilizer maybe. but dont understand why the immobilizer would cause me to not be able to communicate with the ecu... any ideas would be greatly appreciated.
Thread
Thread Starter
Forum
Replies
Last Post
Jet Jockey/A4 Pilot
A4 (B6 Platform) Discussion
2
Apr 16, 2006 12:57 PM
DC_94S4
Audi Original "S" Cars
0
Oct 2, 2004 11:02 AM
