Oil pressure warning & Autocheck system

[archiboy24]

Anyone know if there is anything else, electrically speaking, that might have an effect on the oil pressure warning system? I've tested the wiring and their corresponding connections between the senders and the instrument cluster/Autocheck as well as the oil pressure gauge. Everything checks out OK but I'm still getting the warning coming on at startup and it doesn't go away despite the analog gauge showing normal pressure. Is there a relay that may be wonky? ECU? Something wierd with the engine speed sender (although tach works fine)? I don't know. It doesn't make sense that the gauge reads normally while the warning system is kicking in. Am I missing something? The wiring for this system is about as basic as it gets, so I can't see where it might have gone wrong.

BTW, I've replaced both oil sensors, autocheck control unit and analog gauge with others that were known to be working with no positive results.

Thanks...

[Vagsport]

Trace the alternator charge output wire (blue). It runs to the oil pressure circuit, i.e the relay under the dash. This blue wire goes just about everywhere in the car, ABS ECU, Motronic ECU, instrument cluster, electric window / sunroof control, electric water pump relay, in fact anywhere a reference is needed to allow the control unit concerned recognise the fact the engine is running. Identify the oil pressure control unit (I think it is marked "oeldruiken" or something like that). It is the tall relay with a slit in the plastic casing. Locate the blue wire running into the plug and check for continuity from the alternator. The easiest way to check this is to run a length of wire directly from the blue wire at the back of the alternator and connect it to the corresponding blue wire on the oil pressure control unit plug. Try running the car this way and see if the problem goes away. If this doesn't help, you'll have to check the rest of the wiring. BTW, the analogue gauge is completely seperate from the autocheck / warning lamp.

Siena

[archiboy24]

Thanks for the reply. Is the oil pressure control relay under the hood on the main fuse panel, or is it on the auxiliary fuse/relay panel under the dash? I was under the impression that cars equipped with the Autocheck warning system didn’t have an oil pressure control relay. Do you have any pictures or diagrams?

[Vagsport]

Don't have any wiring diagrams, but the oil pressure control unit is on the auxillary relay panel under the dash, over here it's on the drivers side, yours might be on your side (left).

Siena

[S2central.net]

Nonsense...

The Autocheck equipped cars have wiring direct from the 1.8bar pressure switch (F1) and the 0.3bar switch (F22) into the Autocheck module. Autocheck uses engine speed info (from the tacho signal) to determine what fault to raise. The pressure sender (G10) is wired direct to the analog guage.

Have you mixed up the wiring on the two-pin sender (F22 and G10) - I did it once and got weirdness until I sussed that.

Wiring to the Autocheck module is via the WHITE 26 pin connector and there are a number of cable interconnect points between the senders and the module. I'd need 3B schematics to give you more info than that. Hope to have those soon...

[Stick Insect]

This may be a useless post but I recall some mention of headlight autocheck wiring affecting the oil pressure relay/display.

This was to do with aftermarket headlight wiring looms.

May or may not be useful.

David

[Vagsport]

Nonsense? Cool, Paul, my apologies for my ignorance.

Siena

[archiboy24]

Nonsense...

Have you mixed up the wiring on the two-pin sender (F22 and G10) - I did it once and got weirdness until I sussed that.

I had the wires connected properly to begin with, but switched them just for the hell of it, but with no results. The senders are ok, as are the wires going from the senders to the Autocheck via the white T26 connector on the gauge pod. The autocheck module is also ok. That's why I'm beginning to suspect that some other electronic component or connection associated with the autocheck (be it the light control module, brake warning, coolant warning or whatever) may be at fault here. I'm going to have to check every component and its wiring to try to get to the bottom of this. Sounds tedious...