ColoradoBrad

I drove the car around, shut it off, then turned on the ignition. Oil temp went to ~200 as expected then after ~7 secs it dropped to 150. I unplugged the 3 wire level sensor, turned on ignition and the oil temp gauge doesn't move from 150 anymore so I know for sure the level sensor also has something to do with the oil temp.

Now, where is the other single wire oil temp sender? The brass thing. I can't find it?


BTW, I used VAG to run cluster diagnostics. The cluster is fine.

ColoradoBrad

Page 14 here is no help:<ul><li><a href="http://www.s4-mtm.com/images/Audi_S4_engine_english.pdf">http://www.s4-mtm.com/images/Audi_S4_engine_english.pdf</a></li></ul>

Brien H

To make this as brief as possible my car has shown similar behavior for quite some time. Turn the ignition on when cold, nada. Drive the car around until warm and the oil temp gauge doesn't move. I can then turn the car off/back on and the oil temp gauge will display for a short time, then fall back to nada. Every once in a blue moon the oil temp will start to display for a brief time.

I purchased the oil temp sensor you have pictured from ECS a while back, which is a standard single wire style oil temp sender that VW/Audi has used for years. When I went stage 3 and had the engine out I searched for the 'old' oil temp sensor with no luck. I could only find what looked like a pressure switch near the oil filter (much larger than the small oil temp sender you have pictured). After I STFA I found a few posts mentioning that the oil temp sender is integrated into the oil level sender. I replaced the oil level thermal sensor (bottom of the pan), and I still had the same symptoms. I've VAG tested the cluster and get full sweep. Below is a screen shot from the Bentley which diagrams the wiring to the oil level 'thermal' sensor. G266 is the sensor and the red and grey wire in the 3rd position should be the signal wire. This wire goes to the 9th position on the brown connector inside the ECU housing box (T10/9). I have tested continuity between the oil level thermal sender and T10/9 and all is good, even if I shake the wires (to check for shorts). T10/9 then connects to the cluster itself via a 32 pin connector (T32a/15). I have not verified proper connectivity between T10/9 and T32a/15 yet.

If you happen to find the location for the smaller oil temp sender, or a solution to this problem, please let me know. I need to check the Bentley again to make sure T32a/15 in the diagram goes to the oil temp gauge in the cluster (I am nearly certain it does, which would support the sender on the oil pan is in fact for the oil temp gauge). Sorry for the long post but perhaps it will help you diagnose your problem.

Diagram
<img src="http://hestia.hmdnsgroup.com/~boosted/misc/S4/OilTempSensor.JPG">&lt;/img&gt;

pink shrimp

readind , and when I replaced it with that new level sensor, it began to work again..
fwiw.

ColoradoBrad

Sorry I didn't get back to you. I've been busy with work crap.

There's no doubt the oil temp is built into the level sensor (see #2 below). The single wire brass plug sensor from ECS doesn't seem to exist on my car. I think page 14 of the S4 self study guide is wrong. http://www.s4-mtm.com/images/Audi_S4_engine_english.pdf


Here's where I'm at so far.

1. Ran the VAG test. Gauge sweeps\holds fine.

2. I put the old OEM sensor in hot water, plug it into G266 plug and gauge stays steady at ~180. Unplug it and the temp drops. Plug back in and it rises. A few ignition cycles and it quits completely. This is consistent with why it got replaced.

3. Bought another new sensor for testing (OEM from dealer). Hot water test acts just like the new installed sensor (non-OEM part BTW). Turn ignition on and it goes to ~180 then drops after ~8 secs. WTF?

So I have 3 sensors:
#1 old OEM sensor - works for minutes or longer
#2 new non-OEM sensor - works for ~8 seconds
#3 new OEM sensor - works for ~8 seconds

Why does old OEM sensor work for minutes at time then stop, but the new sensors only work for ~8 seconds. This is weird.

After my testing, I got an P1606 rough road ABS code that is persistent. I'm assuming this is just coincident with the thermal sensor problem and my ABS module is fubar... or ECU going bad.

I think I'm going to borrow my friends S4 and build a harness to connect up the thermal sensors to one another. This would help troubleshooting.

I really need to get a Bentley.

ColoradoBrad

I checked a few more things...

The connector wires at the sensor.
Pin1 - 12V - ok
Pin2 - Ground - ok
Pin3 - Signal Continuity to ecu\cluster - ok

Pin3 goes to the red/gray wire in one of the 10 pin connectors in the ECU box. Then from there it goes to the green connector on the back of the cluster. It's the purple wire at position 15.

Regarding the VAG cluster test... I assumed the ECU controlled the test signals that go to the cluster. This can't be the case for oil temp signal since the path from the G266 connector to the cluster does not include the ECU. The test controller must be embedded in the cluster. My guess is that the test signals and the real signals get MUX'd to the gauge. So if the real signal path (prior to the MUX) has a problem it escapes the VAG cluster test.

I'm going to swap the cluster with my friend's later this week. I'll report back.

ColoradoBrad

Ok. I know that G266 is wired to switched 12V, ground, and to the cluster (T32A/15 green AMP Connector\purple wire) - wiring is good.

Sensor is new and another cluster does the same crap.

Is it possible that a bad ECU is talking to the cluster and telling the oil temp gauge to be an ******* ? E.g. noise or bad signals on comm bus?

Will swap ECUs with a friend next week and report back.

Brien H

You've tried everything I have tried and then some. I'd be suprised if the ECU fixes the problem but you never know. The reason I say this is because I had the problem before going stage 3 with my OEM A box ECU. When going stage 3 I bought a separate ECU and had it flashed to M box code, and I still have the problem. Two different ECUs, same issue.

I have been slammed with work and other projects so haven't had much time to devote to the S4, but I'll try and get out there again this weekend.

Thanks again and keep at it.

ColoradoBrad

In short...

Febi's sensor doesn't work in MY2000 cars

The OEM Audi part made by Hella is the only one that works.<ul><li><a href="https://forums.audiworld.com/s4/msgs/2853377.phtml">More info here</a></li></ul>

LaserAvantS4

wow! it's been a while. glad you sort it out