Intermittent fault on 940 2.0 turbo 1992
 

Good evening everyone I am hoping i can pick your collective brains as I have a really annoying fault on my 940 2.0 turbo. Intermittently and more often than not the car will not start, I have checked the fault codes and am getting 223 and 224 this pointed me to the ECT which i have replaced but it hasn't made any difference whats confusing me is randomly the car will run great does any one have any advice on where to start troubleshooting?

First, i hope you haven't thrown the original sensor away?

Second, unplug the new one, go for a drive - has the temp gauge stopped working? If so, you changed the wrong one!

The correct one is further back along the block.

There are two sensors on my B200F.
 

Quite some time ago I was surprised when an older guy, but not quite as old as me, who had worked on 940s when they were new advised me that they had two engine coolant temperature sensors. One talks to the instrument panel engine temp. gauge and the other talks to the ECU.
On my B200F they are located on the left side of the engine under the induction mankfold. IIRC the one for the ECU is the one towards the rear of the engine and is the most difficult to access.

I don't normallly pick up on peoples typos Ian (i make enough of my own i have to confess!) but that one made me laugh! Thanks for that! :tounge_smile:

I would think the OP has a B200FT at a guess but the two coolant sensors are in the same place., hence my little test outlined in my post above.

Thanks for responding guys, Just to confirm I have changed the harder to reach one from the back of the engine rather than the one at the front which controls the temperature gauge. I have also kept the old one just incase.

Does anyone have a wiring diagram so i can test the connectivity if i understand correctly there are three connectors ground thought the block and then two wires off to ........

.............. the LH-Jetronic 2.4 ECU and the ignition ECU. This is assuming the correct sensor has been supplied!

In the sensor for the temp gauge, there is no earth connection through the case on the sensor, it is simply a thermistor between the two terminals.

On the engine ECU temp sensor, there are two thermistors, one end of each is commoned to earth and the other ends respectively go to the terminals on the sensor.

http://www.myvolvolibrary.info/Tech_...Y94_Wiring.pdf

Assuming you have a cat on your car, that should be the nearest i can find.

Out of curiosity, what brand sensor did you buy? :thinking:

Isn’t code 2-2-3 to do with the idle air control valve rather than the engine coolant sensor which is 2-2-4. It might be worth checking the condition of the former, which often benefits from being cleaned with carb cleaner.

Thats interesting, If i read that correctly there is a red and black wire thats common to the engine temp sensor and the idle air valve and i have fault codes on both of these. Am i reading this diagram correctly?

If i remember correctly it was an intermotor sensor as thats the only one they had in stock.

I have cleaned the idle air valve fairly recently but will give it another go just incase.

You're not reading the diagram correctly, no. One of those is an ECU earth, the other is the ECU control to the EICV.

Before we go any further, where does the Temp gauge sit after driving 4-5 miles from cold?

Just My Two pence worth on this problem the 940 have three inherent problems its prone to overfueling loss of spark and lean mixture
coolant sensor should read 3.5v cold 0.5-1v hot this is a dual sensor with chassis earth
air mass meter variable according to load 1.7v static ignition on 2.7v at idle 3.2v at 3000rpm
injector resistor pack battery voltage input from main relay approx 9v output only when injector on
the coil on this car suffers water ingress wash it carefully there is a external amplifier behind the n/s headlight with the socket facing up make sure the rubber boot is secure and terminals nice and clean pack it with vaseline or something similiar
As other members have said who will no doubt be more experienced than me take their comments on board and finally check your ignition components hope you get it sorted -------Louise