Need wiring help

[emmasweeny]

My car won't run but for a few seconds and throws a CEL, #12 which is the starter switch. I just replaced that with no change in behavior. I'd like to know what the other wires connected to my key switch do and how I could check them for proper operation. Could someone point me to a wiring schematic or tell me what how I can check the other three connections to the keyswitch.

Thanks much.

[Trevor]

Originally Posted by emmasweeny

My car won't run but for a few seconds and throws a CEL, #12 which is the starter switch. I just replaced that with no change in behavior. I'd like to know what the other wires connected to my key switch do and how I could check them for proper operation. Could someone point me to a wiring schematic or tell me what how I can check the other three connections to the keyswitch.

Thanks much.

By starter switch as defined by the manuals, I presume you are referring to the solenoid which is part of the starter motor assembly.

The operating circuit goes via the inhibitor switch, the security unit and whatever. There appears to be several variations between models. Several threads have covered the topic.

First check that you are getting battery voltage at the spade terminal on the solenoid. If not suspect the ignition switch. A very recent thread/post has recorded mechanical problems and loose mounting bolts affecting contact, something which has been reported before.

Do a search and I regret to say, possibly become confused. You will have to use your own initiative.

P.S. I have read the thread again and it would appear that your car starts OK but then will not run. If so, as per the next thread, this is in all respects very strange. Is it that the starter is not disengaging after you release the key? Do you hear anything strange when the car runs for a few seconds?

[b3lha]

Code 12 is unusual.

May I respectfully suggest that you try clearing the codes and then check again to ensure that your error code is definitely a 12.

[emmasweeny]

I didn't beleive the code either but I've eliminated most other possibilities. It will start and run - for a few seconds. Then it's like the switch is turned off. The piece I've replaced is the one that carries all the amps at the opposite end of the key switch.
I have a '92 if that helps.

[Trevor]

Originally Posted by emmasweeny

I didn't beleive the code either but I've eliminated most other possibilities. It will start and run - for a few seconds. Then it's like the switch is turned off. The piece I've replaced is the one that carries all the amps at the opposite end of the key switch.
I have a '92 if that helps.

You say "Then it's like the switch is turned off."

As I mentioned in an earlier post. "If not suspect the ignition switch. A very recent thread/post has recorded mechanical problems and loose mounting bolts affecting contact, something which has been reported before."

Do not doubt your own thoughts, you could very well be correct.

[emmasweeny]

But this is exactly what I've done. I replaced the main ignition contacts opposite the key but there's another three pair on the key side to various contacts and my original questions is what they do so I can check that they're doing what they are supposed to.

[kwren]

Originally Posted by emmasweeny

But this is exactly what I've done. I replaced the main ignition contacts opposite the key but there's another three pair on the key side to various contacts and my original questions is what they do so I can check that they're doing what they are supposed to.

If your engine starts... and runs for a few seconds, it probably is not related to your ignition switch... and chances are it is not an electrical problem.

[kwren]

Originally Posted by kwren

If your engine starts... and runs for a few seconds, it probably is not related to your ignition switch... and chances are it is not an electrical problem.

If you turn your ignition to the "on" position... turn on the head lights, and if they come on and stay on your ignition switch is doing it's thing. All the things that birmally function with the ignition switch on come through the switch in the on position with a 45 amp slow blow fuse and that will eliminate your concern about your ignition switch. Again, this problem may not be electrical at all.

If the headlights work, more tests information is needed in a different direction.

Keith

[TomsSVX]

Kwren is onto something here... More or less, i want to know that your main relay is staying on... Let me dig into schematics and get back

Tom

[TomsSVX]

Ok below are attachments of the pin identifier and the pin voltages... What you should be checking is connector b60 pin 12 to see what happens with voltage there when the engine dies... If it drops, you need to trace the wire back to its origin to try and find the issue.

BTW they are scans so please bear with me here

Tom

[b3lha]

I think code 12 relates to the "starter" pin of the ECU (b61#10) that gets 12v when the key is in the start (cranking) position. The ECU only expects to see voltage on this pin when the engine is cranking, if it sees voltage at any other time it sets the code 12. I think it assumes the engine is cranking when the rpm matches the the speed of the starter motor. This is just an educated guess, I haven't properly analysed the exact conditions that trigger this code.

The FSM says that if the starter motor is working then check the switch and the wiring between the switch and ECU. If the starter motor is not working, check the Inhibitor Switch, Starter and Security System and the wires that run between them.

[TomsSVX]

Maybe the contacts are sticking... but the god awful sound the starter makes when it drags would be apparent. Time to start testing voltages... thats why I posted the whole page

Tom

[Trevor]

Phil, please note.

The information now posted by the helpful crew, does indicate a situation whereby code 12 has been triggered. If so the ECU could be set up to subsequently shut down the engine in order to prevent damage to the starter motor and gear. All would then fall into line. This could be happening as follows:-

In the event that the solenoid became jammed and the armature not released, a back feed via the pull-in coil, would result in positive volts appearing at the solenoid energising circuit, even after the key start contacts had opened. As as a result there would be voltage on the line to the ECU and this could easily be interpreted and utilised to shut down the engine and record a code.

It may assist those not in the know, if I detail what is involved.

Modern starters with an integral solenoid are rather complicated. The solenoid has mechanical and electrical functions and is provided with two separate windings, forming a low impedance pull-in and a high impedance hold coil. The pull-in winding is arranged so that its negative connection is grounded via the starter motor, while the hold winding is directly grounded.

When the starter button is pressed both windings become energised and the solenoid armature moves quickly forward operating a shift lever to engage the pinion with the fly wheel gear. The starter is also energised at reduced voltage via the pull-in winding and starts to rotate so as to assist the gears to mesh.

When the solenoid is fully home and the gears are meshed, heavy contacts are closed to fully energise the starter motor directly from the battery and thus crank the engine. At this point the pull-in coil negative connection become connected to positive via the same heavy contacts, so that current through this coil ceases. With the solenoid fully closed only the hold-coil is required to hold the armature in position and operating current is reduced.

When the start key contact is opened, the hold winding is deenergised, the heavy contacts open and the pull-in winding is returned to ground, thus shunting the pull-in coil. This accelerates the collapse of the magnetic field so as to quickly fully release the solenoid armature. With the solenoid released and the heavy contacts open, the starter motor is deenergised and the pinion is withdrawn from mesh.

It will be seen that with the armature jammed and the heavy contacts closed, battery voltage will remain applied to the initiating circuit via the pull-in winding, even when the start control circuit is open. At this point the starter motor will of course be running, but a one way clutch arrangement is incorporated to mechanically isolate the drive. Thus all could be well for a short period, provided that the ECU shuts down the engine.

Tom, ---- Granted there will be noise, but has this been noticed.

I assure those who have tended to point a finger re copy and paste, that the above text is novel, and is compiled from existing personal knowledge.

[kwren]

Hello there Trevor!
Hopefully I have your permission to copy-paste it for my SVX file? Great and helpful information.

I knew the operation of the starter components and the whys that cause them to do each function in the starters operation, but didn't know about the connection to shut down the engine. Thanks for sharing.

I don't know a lot about the codes and rely on the expert code people on the form. When putting together the knowledge from everyone here, we have a vast world of information. I for one are very appreciative of that.

Many times it takes a bit of time to sort out exactly what applies to each of out individual problems.

If this happened 50 years ago, I would say check for starvation of fuel. A fuel delivery problem? And of course, many things are involved in that.

But we do have that "starter" code!

Just a thought....

Take care,
Keith

[b3lha]

So the consensus is...we think the starter solenoid might be faulty?