Mk3 Cavalier Owners Club | Vauxhall Cavalier Dot Com

Hi guys, im new to this forum. I recently bought a 1972 opel GT with a X20XEV engine in it. Unfortunately is does not have a OBD port for diagnostics (as i guess it was cut out when the engine was put in), would it be possible to wire one in? Thanks gerry

Hi Gerry,

It is quite easy to wire one in, as the wires were originally found in the loom, assuming it has not been modified.
BUT
Do you know what car the loom came from?
Cavalier,
Calibra,
Vectra-B
Or
Omega-B.

And what version of Simtec 56 you are running?
56.0
56.1 or
56.5?

I know it does sound odd, but I recently made up / converted an XEV loom, and the pin-out is completely different for the four different models.
Cavalier = version 1 = Simtec 56.0
Calibra = versions 1 and 2 = Simtec 56.0 and 56.1
Vectra-B = versions 2 and 3 = Simtec 56.1 and 56.5
Omega-B = a variation on version 3 = Simtec 56.5.
------‐----------

Not sure if you have looked at your loom but...

Cavalier and earlier Calibra have just one double relay for the fuel pump.

Later Calibra, Vectra-B and Omega have two 4-pin relays.
One for fuel pump, the other for ECU electrics, (sensors and injectors.)
-----------
Now to really scratch my brain.

Identifying the OBD wires.

Cavalier and Early Calibra use the 10-pin ALDLconnector.

Later Calibra, Vectra-B and Omega,B use the 16-pin EOBD socket.

The wiring is easy to convert for either diagnostic tool.

Secondary thought.
Chances are -
Rather than the wires being cut out, most likely the Opel GT does not have the body loom for the diagnostics plug.
Therefore, never connected up rather than cut out..
Just one of three small square connectors on the Cavalier. (The green one - see image below - top tight connector).

Going back to the ECU.
ALL ECU connectors have 55 pins.

On the Cavalier / Early Calibra.
The Brown / white K-Line Diagnostic wire is on pin 55
The Brown / Yellow L-Line / Excitation wire is on pin 13

On Later Calibra, Vectra-B and Omega-B.
The Brown / white K-Line Diagnostic wire is on pin 1
The Brown / Yellow L-Line / Excitation wire is on pin 22.
--‐-------------------

Okay -

Cavalier and Early Calibra 10-Pin ALDL connection.
Via a small green, square connector x11





to ALDL plug x13



If the ALDLsystem, diagnostics is via...
1 - Tech 1 or Tech 2 with adapter.
2 - AutoScanner Opel / Opel Scanner
3 - Very late versions of VauxCom / OpCom.
4 - Can be flashed out on the dash

Wiring for ALDL Plug.
Pin A = Brown to Ground.
Pin B = Brown / Yellow to Excitation Line.
Pin F = Red to fused battery live feed
Pin G = Brown / White to K-Line diagnostic line.

To flash out codes on the dash engine light (if you have one).
Short pins A & B together.
In normal running, pins A and G should be shorted together.

---------------------------------------
If EOBD 16-Pin System

1 - Tech 2
2 - Mid to late versions of VauxCom / OpCom.
3 - Various Generic code readers (EOBD / EOBD2 compliant).

Wiring for EOBD / EOBD2 16 Pin Connector



Pin 4 = Brown = Diagnostic Tool Ground
Pin 5 = Brown = Diagnostic Signal Ground
(Join 4 and 5 together).
Pin 6 =Brown / Yellow = L-Line Excitation Wire
Pin 7 = Brown / White = K-Line Diagnostic Wire
Pin 16 = Red = Fused 12 volt battery live feed.

I hope that helps.

Cheers,
Rob.

Additional note - if you need to add an engine warning light, it is wired as follows.

Fused Ignition live to standard 12v 1.2watt bulb (or 12v led + terminal).
Normally a black wire for ignition live.

From 12v bulb (12v led negative terminal) to x11 connector.
Brown / Blue wire which is grounded by the ECU with ignition on, not running (bulb check),
And when an engine fault is present.

If you have the square green connector, then you are good to go as all three diagnostics wires are there.

Pin 4 - Brown / Yellow - L-Line Excitation (code flash wire).
Pin 5 - Brown / White - K-Line Diagnostic wire.
Pin 6 - Brown / Blue - EML / MIL Light ground trigger from the ECU.

Hi Rob, thanks for your reply's. The car the engine came out of was a Vectra, how do i work out what version of simtec the car has? Shall I take a photo of the big plug that goes into the ECU? Thanks for the info so far, very helpful. So do I understand right that basically i need to find 2-3 wires from the loom to then connect to a diagnostic plug? where can i get a plug from? thanks

If it is a from a Vectra-B, then you are looking at the later version of Simtec.
Probably 56.5.

There should be a bunch of numbers or letters on the ECU cover.
There is a 2 letter (alpha) code - possibly RS or RT if it is Vectra...
It may even say Simtec 56.1 or Simtec 56.6 on it.

The loom should have a large connector, with at least 25 or 26 pins in it. Unless it was cut off by the previous owner. Identified as X7
The vectra will not have the three small connectors.

The diagnostic wires in X7 are :-
Pin 3 - brown / white to diagnostic pin 7
Pin 4 - brown / yellow to diagnostic pin 6

The diagnostic plug is an international standard item referred to as an EOBD or EOBD2 16 pin plug.
Every European car manuafactured from 1996 onwards will be supplied with one of them.

So, take your pick from a scrap yard.
Or see if anything is available from ebay... etc.

------------------------

As mentioned
You only need 5 pins, or 4 wires.

Pins 4 and 5 (linked) - brown wire for ground or battery negative.

Pin 6 - brown / yellow - excitation line.

Pin 7 - brown / white - K Line disgnostic wire.

Pin 16 - red - Battery Positive, +12v line.

---------------------------

For the engine management light.

This is also fed by the same x7 connector.

Ignition live to positive side of the bulb / 12v led.

Brown / blue wire on x7 pin 5 to the negative side of the bulb or 12v led.

The ECU acts as the ground trigger to illuminate the bulb / led.

Hi, thanks for your reply, so the ECU is a 56.0. I have some pics of the plug and wires. I want to attach some photos for you, how do i do this? thanks gerry

You need to use a picture hosting site, and then put a link in the text of your post.

Here are some hosts and how to use them.

PostImages -
https://www.vauxhallcavalier.com/forum/ ... =7&t=16827

Flikr -
https://www.vauxhallcavalier.com/forum/ ... =7&t=16077

Photobucket -
https://www.vauxhallcavalier.com/forum/ ... =7&t=14778

goopelgt wrote: ↑Sat May 13, 2023 7:42 pm Hi, thanks for your reply, so the ECU is a 56.0. I have some pics of the plug and wires.

Yes it would be good to see pictures of your plugs, because the ECU from a Vectra-B should not be a Siemens Simtec 56.0.

Unless it is a non-UK Vectra-A. (Cavalier in the UK).

Hi, the chap I bought the car from got the original ecu wet, so got another and had the immobiliser removed from it as I didn’t want it. (There was a key taped to the immobiliser ring)Is there any chance you can contact me via cadora woods glamping? I have a lot of questions! Do you think it is a problem that I have 56.0 ? Thanks

How would I contact you via a campsite?

If you have a Vectra-B loom, but a Cavalier mk3 / Vectra-A ECU, then yes you have a huge problem.

They are wired up completely differently.

Hi, all my contact details are on there. I have never been on a forum before, wasn’t sure if I can/should put my phone number on here ? Thanks

Ah okay... it is a bit odd, but I see your details on the website.
It looks amazingly tranquil.

You can email me directly if that helps.
But we do not recommend posting names, and contact details on a public facing forum.

You have an email at the forum registered email address.

The important bit is to verify exactly what you have.

Which loom,
Which ECU,

Ensure you have the matched transponder key and immobiliser ring, and probably the alarm unit too.

I sense a bit of deja-vu but in reverse from the following recent thread.

viewtopic.php?f=15&t=17223

Apologies to other forum members, it appears that the issue is a popping exhaust when revving, but quite a smooth idle.

My own thoughts are possibly a partially blocked exhaust.
Being an XEV the knock sensor should control the timing, so hopefully rule that out.

Other than that, dirty fuel; however, I suspect it would pop at idle too if the fuel was contaminated.