ECU plug additional wiring prob?

subanator · Post by **subanator** » Thu Aug 10, 2006 12:32 am

I have a N/A wiring loom with the EA82T turbo ECU.
I now get 2x faults, Knock sensor and waste gate solenoid.

I have a plug to knock sensor, but no wiring to the ECU, so can I wire this into the N/A ECU plug?? It has no pin, do I need to get another plug and prise out a pin and solder it in its correct pinout?

As for the Waste Gate Solenoid, I dont have one as its vacuum/boost controlled wastegate. Do I need to dummy value to ground to equal a soleniod? Or do I just connect a solenoid as a load? Same prob with no pin for plug pinout.

Anyone see another way around this??

Craigus · Post by **Craigus** » Thu Aug 10, 2006 7:05 am

I take it this is the 4 plug ECU?

Is the engine actually running OK?

subanator · Post by **subanator** » Fri Aug 11, 2006 11:34 pm

Craigus wrote:I take it this is the 4 plug ECU?

Is the engine actually running OK?

Yes 4 plug, Yes runs fine, doesnt retard power with fault codes.
No pinging, had air/fuel checked at 12.3:1 under boost, just want insurance and fault lights cleared to see a real prob when it occurs.

Gannon · Post by **Gannon** » Sat Aug 12, 2006 7:45 am

Same 2 codes as i had.
I take it you have the turbo engine harness plugged into the NA wiring loom.
There is a wire in i think the white loom plug that isnt connected. i will take a pic to show you.
Wastegate solenoid will not effect operation of car. it is an altitude compensator and increases boost pressure at at high altitudes due to lower air density. or something like that.
If car runs, dont worry about it.

Gannon

Gannon · Post by **Gannon** » Sat Aug 12, 2006 10:12 am

I had a quick look.
The white engine plug, loom side, pin 14 is knock sensor. Have you got the ea82servicemanualpart2.pdf the wiring diagrams will show what pin it is.
Check for this wire,.. i think it is white or white/black. My touring wagon is an 89 MPFI, and it had the knock sensor wire in the loom.

Only thing is i never got it running. Damn headgasket:mad:

To test the knock sensor, grab a timing light... and with the engine running, tap the knock sensor lightly with a hammer, it should retard the timing.
What ecu are you using?

I read on the usmb that the wastegate not connected will cause the car to not start at all. And i assume that that is why i couldnt get mine started with the turbo ecu, but i did with the MPFI ecu.

Gannon

subanator · Post by **subanator** » Sun Aug 13, 2006 11:36 pm

Interesting info Gannon. It should be simple enough to do, just want to get rid of the damn fault light. Rather have a genuine fault warning if it occurs

I will have a good look at the wiring and the plug tomorrow. I have a MPFI N/A wiring harness and a turbo ECU. I also have a short harness off a 3 plug ECU engine that is the plug for the knock sensor (earlier 3 plug ones had a remote knock sensor controller - not in the ECU). All I have to do is cut and splice this to the 4 plug ECU, maybe by the plug you showed, or I can bypass it directly with a nice piece of 3 core shielded cable I have??

subanator · Post by **subanator** » Tue Aug 15, 2006 11:31 pm

Have to put some effort into this next weekend now - been too bloody sick with the flu.

stamp_licker · Post by **stamp_licker** » Wed Aug 16, 2006 2:01 pm

the early knock units did the advance retard at the dist which is different to the later dist running of a 4 plug ecu.that is 4 plug dist is a photo diode etc controlled by the ecu.3 plug dist control by vacuum.when i did mine i just used a n/a ecu [4 plug] to power the turbo engine no probs.

subanator · Post by **subanator** » Sat Aug 19, 2006 12:24 am

By the picture and what Suparoo is saying is correct, the arrow to that wire did throw me a bit for a while! Its not that one, but found as stated PIN 14 in that plug. This is the stock MPFI wiring harness in the body, and goes to PIN 36 ECU ok.

However, cos my engine harness is N/A is doesnt have wiring to that pin(s), only blanks. Just need to get an old harness to pick some pins out of - anyone??

The other thing is the knock sensor harness from the 3 plug ECU (having a separate knock control unit) runs to the distibuter harness, and is not compatible, so a cut and slice is required. I know the knock sensor is Piezeo (spelling?) and has 2x wires, red and green with an overall screen. But by the 4 plug ECU wiring diagram all you need is one wire and screen.

What is the other wire for? In the 3 plug ECU drawing, it runs both wires back to the knock controller. Now I am not sure just what wire is need for the 4 plug ECU.

Measurements taken has the red wire pin in sensor reading Meg ohms to body, and the green wire clear. However my ECU has detected no sensor connected, so maybe there is some resistance measured, or leakage current etc to detect? The other wire the signal? It is self generating voltage right? I will be now doing some research on how these things work.

Havent worked out to dummy the wategate solenoid fault yet, have to find that wire too.

Diagram in like explains:
http://www.picotech.com/auto/articles/knock-sensor.html

Gannon · Post by **Gannon** » Sat Aug 19, 2006 6:27 pm

My knock sensor only has one wire, it is green.
yah sorry about the arrow on the picture, the arrow points to the rubber gromit that has to be removed to take out the pins in the plug.

Im pretty sure that the piezo should have a Mohms reading and if you tap the block with a hammer near the knock sensor, the reading should change.

subanator · Post by **subanator** » Sun Aug 20, 2006 11:54 pm

Ok, a trip to the wrecker answered a few questions, but not a solution.

The single wire knock sensor must have been in the 4 plug ECU motors, cos I found an engine harness and plug for that turbo model. Will consider getting this if I can get a single wire sensor, as there were no motors there.

The 2x wire knock sensor must have in the 3 plug ECU engine, as thats what is fitted to mine via a 4 plug ECU and dizzy.

Reading some web info it suggests to connect one of the wires + screen and test, and if it didnt work, try the other. I am shit scared if I get the wrong one it will cause a prob in the ECU, maybe it will do nothing? Or get another sensor with one wire + the other engine harness? That way the pinout with plug prob is solved.

Craigus · Post by **Craigus** » Mon Aug 21, 2006 6:22 pm

I am shit scared if I get the wrong one it will cause a prob in the ECU,

While I can't 100% guarantee anything, I think that is really very unlikely. The knock sensor is just a specialised piezoelectric microphone, with a very high source impedance. The ECU input will similarly be a high impedance input and unlikely to be damaged by an incorrectly connected knock sensor. What may happen is that the ECU will detect that the expected sensor is not connected and throw up an error code, and yes, it may not work as expected either.

Gannon · Post by **Gannon** » Mon Aug 21, 2006 6:38 pm

The knock sensor is a piezo-electric device that produces a small voltage when it vibrates, much the same as most audio microphones.

Some piezo mikes have 2 wires, one for positive signal, the other for shield/negative.
Others are balanced and have 3 wires, one for positive signal, one for negative signal and the last is the shield

Try connecting a multimeter on mV range and lightly tap the sensor, it might show something, if that doesnt work can you access an ociloscope, it should show you a signal.

I doubt that connecting it will damage anything, as its output is only a few mV. The two wires on the knock sensor are all you need to try, the ground of the sensor is connected through the chassis i think (i will check that)

Good luck

subanator · Post by **subanator** » Mon Aug 21, 2006 11:10 pm

Thanks for the update guys, seems I should have got that turbo engine harness, and then should give it a go. I will give that test with a multimeter, a scopemeter at work is around somewhere should I need it!