URs4 engine trouble

[Gormj]

Ok, but have you checked G28 with a scope?
Is there fuel but no spark?
Have you tried if the car starts when towing it in gear?


Could be, but the likelyhood is very low, that's why it's better to check everything else first.

Is it possible for you to take an ECU from another car temporarily (551A/551AA/551B) and try if your car starts with that ECU?
If it does, then you will indeed need to replace the ECU, but as I said before, 551C will not work without modification.

Have not tried with a scope on G28, but have changed it to another one (used but should be working).

It is getting fuel on all 5 cylinders.

Have not tried towing the car.

[prj]

If it's getting fuel, it should be sparking as well.
Towing you can always try and then gently engaging it into gear...
At the same time you could check in VAG-COM what the values are like.

[S2central.net]

Have a look here on 'no start' issues.... I am working on a more detailed doc for this.

If you are getting fuel then it proves ECU is powered, G28 is good, ECU is activating Fuel pump relay (FPRy) and the FPRy is working.

You now need to see if injectors are getting 12V supply.

Then check if G4 and G40 are healthy and aligned correctly.... If they aren't you won't get spark (or injector pulses) as the ECU doesn't know where the pistons and camshafts are in the cycle.

[S2central.net]

LINKY to helpful sticky ---> http://www.s2forum.com/forum/showthread.php?t=49771

[prj]

The odd thing is though, that he tried the ECU on another car and that car didn't start.
Something tells me that the fault might be inside the ECU, because you can swap non-immo ECU's and the other car should start. Auto or not.

Easiest to check is to put another ECU on the car temporarily from a non-immo car, even from an automatic.

In case it is fried, I have a spare ECU (well a few actually ), so I offered that as well.

[Gormj]

I have just been in the car checking a couple of things

Connection from G28 to ECU = OK
When disconnecting G4 and G40 I get an error in the ECU (disconnect or short)
Group 000 readout
1 = 000
2 = 000
3 = 000
4 = 128
5 = 060
6 = 128
7 = 048
8 = 128
9 = 128
10 = 000

Injectors are firing (can see gasoline vapor from all 5 sparkplug holes when they are removed and turning the starter, looks like the correct firing order too)

S2central> I will look at your link and see if I have missed anything.

I appriciate all the help I am getting here (I am bit tired of driving in a Opel/Vaxhall)

[S2central.net]

DO the LED test on G40 - it proves it is alive at least, but you will need a scope to check if it arrives at the right time wrt G4.

2-channel oscilloscope required to do this properly, but meantime have a check that timing belt and alignment is OK.

[Gormj]

I did a LED test on the G4, and I can see it breaks the signal once every turn of the camshaft, timming belt is alligned correct.

I need to dig out my old scope from back of my storage room so I can test the G4 ;-)

Edit> "I did a LED test on the G4" should have been "I did a LED test on the G40"

[S2central.net]

Oh if you have a scope then its dead easy - search here for what the waveform should look like... Or post a pic of yours and I'll have a look.

Measure G4 AND G40 at same time so you can see alignment.

Of course you also have to ensure all those signals are getting into the ECU as well.

While you are at it - with the key ON do you see +12V on one side of the fuel injectors ?

[UrS4boy]

...While you are at it - with the key ON do you see +12V on one side of the fuel injectors ?

Paul: Have we not agreed that the AAN injectors (N30, 31, 32, 33 and 83) will NOT see their 12V feed voltage from the S72 fuse until the AAN J17 fuel pump relay has been triggered by the AAN ECU (via pin 3) after the ECU is happy with both the G40 cam sensor and G4 crank position sensor signals?

[S2central.net]

No we didn't agree - ABY pulls pin 37 to 12v when key is on. I need to annotate a schematic so you can see this better. I didn't look at proper AAN diagrams yet - cannot trust the diagrams from training books. Do you have a bentley schematic for AAN you can scan there?

[Gormj]

I have an AAN schematic from Bentley Publishers, I will try to scan it

[UrS4boy]

No we didn't agree - ABY pulls pin 37 to 12v when key is on. I need to annotate a schematic so you can see this better. I didn't look at proper AAN diagrams yet - cannot trust the diagrams from training books. Do you have a bentley schematic for AAN you can scan there?

Okay. We are agreeing that we are not agreeing.

But remember the patient *is* an AAN in a C4 chassis, not an ABY in a B4. That could be the difference.

I will work on scanning the AAN version of the Bentley that is in my hand.

Dave F.

[UrS4boy]

AAN Ignition ECU diagrams

See pdf attached. Here are my comments on the diagrams:

Comments on AAN ECU Ignition Diagrams

General: Constant power on track 30 of the bus; switched power = track 15 on the Bus.

Page 23 (X51)
Power flows to the Coils via switched power S3/15 (via [21] to [17] to circuit breaker S64. This feeds the five coils on line (d) as well as Pin 27/55 in the ECU. (D94) is listed as “plus connection (circuit breaker for CFI System) in engine compartment wiring harness”
Note: G70 Mass Air Flow (MAF) sensor pin 5 on track [19] is fed from track [43] (on page25 (X53)

Page 24 (X52).
ECU is fed constant power via Bus 30 through Fuse S26 to pin T18/55.
ECU is controlling the POSs and current through the coils to ground via pins T20/55, T21/55, T2/55, T1/55 and T23/55. (Note: there is an error in Bentley’s diagram of the N127 POS)

Page 25 (X53)
Pin T3/55 energizes the J17 Fuel Pump Relay (takes switched power to ground to pull the relay on). This provides power to 87F and 87A. 87F splits the power to S2/87F on the left of the diagram (track [44]) which goes to track [265] (not shown here) which is the S17 fuse powering the G6 fuel pump, and also to 87F/TDI which goes to circuit breaker S73 on track [51] that goes to track [59] on Page 26 (X54) to power the O2 sensor heater. The 87A pin on the relay leaves page 25 (53) on line (e) and goes all the way to page 29 (X57). Power from 87A returns to page 25 (X53) on track [44] via track [104] to Circuit Breaker 72 which provides power to the injectors and the MAF track [19]

Page 26 (X54)
Nothing pertinent to the basic starting and running of the engine

Page 27 (X55)
Shows G4 Crank position, G28 engine speed and G61 knock sensor 1

Page 28 (X56)
Shows the G66 knock sensor 2, G42 Intake Air Temp and G62 engine coolant temp sensors

Page 29 (X57)
At the top, shows line (e) bring power to Pin S3/87a of the fuel pump relay, which then outputs on track [105] to track [44] on Page 25 (X53) which is the S72 breaker for the fuel injector and MAF power, as well as from 87a on track [105] to Circuit Breaker S75 that provides power to the N75 WGFV, the N80 Evaporative emissions canister valve and the N71 ISV.
Also shows the G40 Hall sender (cam position sender) and the G16 Pressure sensor.

[prj]

Okay. We are agreeing that we are not agreeing.

But remember the patient *is* an AAN in a C4 chassis, not an ABY in a B4. That could be the difference.

I will work on scanning the AAN version of the Bentley that is in my hand.

Dave F.

Uhm, considering I have this AAN ecu next to my computer:


Shall I just measure PIN 37 on the ECU when the ECU is on and end the debate?