Coolant temperature sensor Audi 100 C4 AAT

Hello!

Has anyone ever measured the target resistance value of the coolant temperature sensor at a 90°C engine temperature? Mine reads 223 ohms at 90°.

'I'm experiencing some jerking during load changes and a relatively rough engine running, but the symptoms disappear when the sensor is disconnected!'

Best regards,
Andi.

Sorry, I forgot to mention which one I'm talking about >> the G62!

Hi Andi, just unplugging the connector doesn't necessarily mean the sensor is defective.
Instead, the system is informed that it is cold, and as a result, the injection timing is shifted towards being earlier.
If I were in your situation, I would check the fuel injection timing.

Hi,
"I won't be able to achieve 90° for the time being. At 80-85°, mine reads 287 ohms. If the sensor is the same type as the one used in the 2.3L gasoline engine, the tolerance range for 90° is 220 to 280 ohms."

Morning!

Okay, I've figured out that my sensor is already close to its tolerance limit, but it's not a major issue. However, I've also noticed something: When I disconnect the solenoid valve for the ESP injection start control, it still makes a knocking sound when the car is stationary, but it runs relatively quietly while driving, and the jerking/shaking is also gone!

A resistance measurement of the solenoid valve yielded 325 ohms .
However, to my knowledge, it should be between 14 and 18 ohms, so I think it's broken!

That would also explain the jerking I experience when changing loads, because the solenoid valve is likely still generating a magnetic field, but only a small one. This means the system then encounters a larger force, but only after a certain amount of time has passed, and then >> Jerk!!

Hi,

Quote:

Vielmehr wird dem Stg mitgeteilt , daß es kalt ist und somit wird die Einspritzung in Richtung früh verschoben.

If the control unit reacts in the same way as the MSA15 from the 1.9 engine, then it will use the value from the fuel temperature sensor as a substitute value when a faulty sensor is detected. This would naturally be the case if the connector is disconnected.

Regards,
dieter

Hi Dieter!

My engine control unit (ECU) uses a pre-programmed value when the sensor is defective or disconnected, at least according to the information in my engine's service manual (SSP).

'Using a coolant temperature sensor as a replacement for a fuel temperature sensor seems a bit odd to me, though.'

Greetings.
Andi.

Hi,

Quote:

Kraftofftemperaturgeber als ersatz für die Kühlmitteltemperatur is aber meines erachtens nach auch ein wenig komisch oder?

Why? The fuel temperature is measured by the ESP system and is therefore somewhat correlated with the coolant temperature. I recently had a faulty coolant temperature sensor, which caused the control unit to constantly believe that the engine was warm. This made it very difficult to start the cold engine. When the sensor was disconnected, the engine started perfectly.

greetings
dieter

Hmm... I can't quite picture that. In my case, the fuel temperature is significantly lower than the coolant temperature (around 50°C versus 90°C).

Best regards, Rainer.

Klar ist die geringer, ist bei mir auch so. Was die Entwickler sich dabei gedacht haben weis ich natürlich auch nicht, aber es steht im RLF und ich habe es ausprobiert, bei abgezogenem Fühler wird im Meßwertblock Kühlmitteltemperatur die Kraftstofftemperatur angezeigt. Bei moderaten Temperaturen ist es ja auch egal, da wird er immer gut anspringen, aber wenn es richtig kalt ist kann er so da noch drauf reagieren. Hilft bloß auch nichts wenn das Stg. nicht merkt, daß der Fühler defekt ist. EiApparently, a plausibility check is not being performed.

Regards,
dieter

I didn't measure the resistance of the solenoid valve, but rather the internal resistance of the motor control unit's power amplifier stage!

So, all my sensors are in perfect working order!

'I'm mainly concerned about the jerking I experience when shifting gears and the vibrations I feel in high gears at full throttle, specifically in the range of 1900-2300 RPM.'

However, I've noticed that these vibrations don't occur during the warm-up phase, i.e., when the gauge is around 60°, or that the load changes are dampened.

I've been searching for the problem for about a year now, but no one can help me (the Bosch service says everything is fine).

Since my timing belt replacement (along with a head gasket replacement) a week ago, it's gotten a little better, but it's still present!