jparry19

I have a 1998 A8 3.7 the cat light is on, and the engine won't start, I've tested everything I can but not seeing any signal from the ECU. Any help would be great.

dallas0029

What tool are you using to attempt to connect? Do you have the original stereo. Cat light usually means the ECU has shut off an injector after sensing missfires i think.

jparry19

Thanks for your reply.
I will try to explain myself better.
I have conected vagcom to the diag port and getting the following

Control Module Part Number: 4D0 907 557 Q
Component and/or Version: 3,7L V8/4V MOTR AT D01
Software Coding: 04153
Work Shop Code: WSC 00000
9 Faults Found:
18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 35-10 - - - Intermittent
17538 - Fuel Trim: Bank 2 (Mult): System too Lean
P1130 - 35-10 - - - Intermittent
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
P1128 - 35-10 - - - Intermittent
16534 - Oxygen (Lambda) Sensor B2 S1: Malfunction in Circuit
P0150 - 35-10 - - - Intermittent
17605 - Oxygen (Lambda) Sensor Heater Circuit: B2 S1: Electrical Malfunction
P1197 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - - Intermittent
16689 - Cylinder 5 Misfire Detected
P0305 - 35-10 - - - Intermittent
17546 - Fuel Trim: Bank 2 (Add): System too Lean
P1138 - 35-10 - - - Intermittent
16686 - Cylinder 2 Misfire Detected
P0302 - 35-10 - - - Intermittent

Then I cleared the faults and started to investigate the problem.
New spark plugs and checked the voltage at the coils and getting 12v. I have connected the multimeter to the output of the ECU for each of the coils and no flicker on the meter. i then checked the fault codes again.

9 Faults Found:
18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 35-10 - - - Intermittent
17917 - Idle Control Valve (N71): Electrical Malfunction
P1509 - 35-00 - -
17817 - EVAP Purge Valve (N80): Electrical Malfunction
P1409 - 35-10 - - - Intermittent
17609 - Fuel Injector for Cylinder 1 (N30): Electrical Malfunction
P1201 - 35-00 - -
17613 - Fuel Injector for Cylinder 5 (N83): Electrical Malfunction
P1205 - 35-00 - -
17612 - Fuel Injector for Cylinder 4 (N33): Electrical Malfunction
P1204 - 35-00 - -
17616 - Fuel Injector for Cylinder 8 (N86): Electrical Malfunction
P1208 - 35-00 - -
17919 - Intake Manifold Valve (N156): Electrical Malfunction
P1511 - 35-00 - -
16944 - System Voltage Malfunction
P0560 - 35-00 - -

Some of these would have been when i had the output stage disconnected. There is no mention of the CAT light. I am wondering if the CAT is blocked if there is anything that would inhibit the ignition system. If the Lambda sensor is faulty could this stop the ignition system.

Any help would be great.