1999 jetta dead ECM?

BACKSTORY, skip to bottom for current problems...

Having some problems with my jetta recently, started to act up this summer while running to work, cruising along in the rain and lost everything. cruise kicked off, no throttle, etc. get to side of road and shut off car and try to restart, no start. car gets towed, and later check wiring from injection pump under battery box, found multiple corroded wires, repaired.

Ran fine for 2-3 months, and then suddenly died again on way to work, left car for a while, came back and started right up, drove to work and bought VCDS. checked codes, read up on forum and ended up resetting injection pump value to stock (was WAY off) and hammer mod to get injection quantity to 5 if I remember correctly.

NOW for the interesting part, its winter now... started car while clearing driveway, while backing up car through a snow pile I kill it/ it dies (its a manual) and will not restart. Pull codes via VCDS, get Bentley manual and troubleshoot, OHM out sensors and wiring, and ended up with probable dead ECM.

ANY help appreciated. sorry for the long backstory...


Saturday,17,February,2018,13:12:07:47695
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 8.1 x64
VCDS Version: 18.2.0.3 (x64) HEX-V2 CB: 0.4411.4
Data version: 20180212 DS287.0
www.Ross-Tech.com


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Chassis Type: 9M - VW Jetta IV (1998 > 2014)
Scan: 01 02 03 08 09 15 16 17 19 22 29 35 36 37 39 46 47 55 56 57
75 76

Mileage: 567800km-352814miles
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Address 01: Engine Labels: 038-906-018-AGR.lbl
Part No: 038 906 018 EB
Component: 1,9l R4 EDC G700SG 2143
Coding: 00002
Shop #: WSC 00066
VCID: 5AEE9A36D504DD275CC-4B3C
6 Faults Found:
16764 - Glow Plug/Heater (Q6) Circuit
P0380 - 35-10 - Malfunction - Intermittent
17664 - Engine Coolant Temp Sensor (G62)
P1256 - 35-10 - Open or Short to Plus - Intermittent
17970 - Quantity Adjuster (N146)
P1562 - 35-10 - Upper Limit Reached - Intermittent
17971 - Quantity Adjuster (N146)
P1563 - 35-10 - Lower Limit Reached - Intermittent
17762 - Modulating Piston Movement Sensor (G149)
P1354 - 35-10 - Electrical Malfunction - Intermittent
17656 - Start of Injection Timing Regulation
P1248 - 35-10 - Control Deviation - Intermittent
Readiness: 1 6 0 0 0

I doubt your ECU is done. Re-check those wires you repaired, check more wiring for damage. Check the ground on top of the transmission and the others under battery and in rain train. Check ECU connects. I think you may find more corroded wires somewhere.
Electrical is tough, I chased one wire (QA) for a year, it passed ohm test but would not carry enough current to work.

^^^ Agreed, clean the grounds listed.

To many devices spread around.

If the ground under the battery tray is bad anything that grounds to the body will not have a good ground.

Also, while you are in the plenum maybe put a piece of aluminum foil over the ECU to run any water off that may drip on it. Leave room for air flow for the ECU.
Clean the drain in there also.

Cleaned all grounds, checked all fuses, tore apart harness from IP to ECM and had no obviously corroded or damaged wiring.

Rechecked wiring by putting 12v to connector for IP and checking on other side at ECM, all checked out by carrying full voltage minus pin 5 on IP 10 pin harness, it was grounded even with ECM disconnected. Ran through Bentley diagrams, trying to trace said wire, but the thing splits off here and gets spliced into there which makes troubleshooting tedious to say the least. Half way finished testing and tracing wiring on car and basically finished up with Bentley wiring diagrams by figuring out where wiring goes.

Also checked G80 (needle lift sensor) and N109 (fuel shut off solenoid) just because and found N109 inop, SO I will be getting a socketed ECM and a new fuel solenoid.

Wiring mess will wait for the moment until both these parts do not fix the problem.

Will post update either way afterwards

Crazykrueger said:

Rechecked wiring by putting 12v to connector for IP and checking on other side at ECM, all checked out by carrying full voltage minus pin 5 on IP 10 pin harness, it was grounded even with ECM disconnected.

Also checked G80 (needle lift sensor) and N109 (fuel shut off solenoid) just because and found N109 inop, SO I will be getting a socketed ECM and a new fuel solenoid.

Wiring mess will wait for the moment until both these parts do not fix the problem.

Click to expand...

I think pin 5 if the power feed to the injection pump. Is it Red/Violet ??
Power from fuse 32. 30 amp.

On N109, no continuity or no power?

My bad on N109, didn't have it grounded (DUH), so it still works, both shutoffs work and ohm out almost the same, so I have a spare now!

Pin 5 is red/violet. It is grounded with key off and back probing connector for IP, possibly grounded through other parts from wiring that splits off harness and runs into dash? Has full power from battery after glow plugs cycle.

Fuse 32 is 15 amp, Bentley says that is correct.

Crazykrueger said:

My bad on N109, didn't have it grounded (DUH), so it still works, both shutoffs work and ohm out almost the same, so I have a spare now!

Pin 5 is red/violet. It is grounded with key off and back probing connector for IP, possibly grounded through other parts from wiring that splits off harness and runs into dash? Has full power from battery after glow plugs cycle.

Fuse 32 is 15 amp, Bentley says that is correct.

Click to expand...

Interesting, my diagram indicates 30 amp but my text list has 15 amp.

OK, power goes to the pump on pin 5, through a coil, out pin 6 to the ECM pins 116 and 121.
I think the ECU grounds inside the plenum from pins 4 & 5. Brown / Red.
With things plugged in, ignition on (not running) I would measure the voltage from the battery negative post (not the clamp) to the wires at pins 4 and 5.
I would not want to see more then a few tenths of a volt.

wonneber said:

Interesting, my diagram indicates 30 amp but my text list has 15 amp.
OK, power goes to the pump on pin 5, through a coil, out pin 6 to the ECM pins 116 and 121.
I think the ECU grounds inside the plenum from pins 4 & 5. Brown / Red.
With things plugged in, ignition on (not running) I would measure the voltage from the battery negative post (not the clamp) to the wires at pins 4 and 5.
I would not want to see more then a few tenths of a volt.

Click to expand...

Yeah that fuse discrepancy is strange...

Your jetta is newer than mine so different pins, but same concept.

Checked that already and found ground on pin 5 with key off, and full battery voltage with key on not running, was concerned with grounding with key off but after looking through wiring found it is tapped into multiple times throughout engine bay and dash so I assumed that the ground was coming from another terminal.

Good news is that I got it running, cleaned up more terminals and temporarily reinstalled battery (really wish I had made battery cable extensions) made sure everything was hooked up. Saw that there was air in the fuel lines between the injectors so pulled return line off thermo t and bled air out, rehooked and it started right up.

Still not sure if I just killed it and lost prime enough to not start or something else, but haven’t had a problem since minus long crank to start due to air getting in somewhere. So now it’s getting a upgraded in tank lift pump and all fuel lines.

Speaking of fuel lines where does one find the plastic return lines between injectors?? Thanks in advance.

Glad you got it running.
Do you think it was a bad ground or the priming the pump?
ID parts has the hose, I don't think they have the cap on the last one.
Original is rubber with the cloth braiding, not plastic.