FC3S 90 NA - Error codes using multimeter?
 

Hi All,

I have a 1990 S5 non-turbo FC3S that has very poor acceleration, I am fairly sure the car is in limp mode, however this particular car has no check engine light in the idiot cluster.

Is there another way to see or hear the codes similar to the S4 method using either LED's, Digital Multimeter or a pezo speaker/buzzer?

It would make my life easier as I otherwise will have to start checking every single component individually until I find something suspicious :scratch:

If the MOP failed, then out took the ecu with it. I was unable to retrieve codes on mine Open the ECU, look and smell for burned stuff. If the power transistor is cooked, you need not perform any more diagnostics. You nred a ECU and MOP or RTEK.

You use the check connector w/two Yellow wires and a Black/White wire (3 wires total) right near the lead coil using the S4 LED light method. There is also a single wire check connector near the lead coil featuring an Orange wire. W/the LED code checker connected to the diagnostic plug (use the Black/White wire in the connector for the voltage source and one of the Yellow wires for the input signal from the ECU). Then ground the Orange wire (to the negative battery terminal) and w/the ignition set to on any error codes will flash. There are two Yellow wires in the check connector to choose from. Not sure exactly which one to use but you'll figure it out.

@satch, Cheers! :icon_tup: fortunately I was able to buy a full set of factory workshop manuals with all suppliments etc for Australian cars, about an hour after I posted this I worked out the pinout using the wiring book and was able to do the test. However I received no codes, just the 3 second light up when you initially turn ign on, then it goes out.

@inflatablepets LOL! Quite the jump from wanting to know how to perform diagnostics to assumed total ECU failure! Though I will keep that in mind as I work through the car, thanks :)

Are you sure you chose the correct Yellow based wire in the 3 wire check connector? To prove that you did you can unplug a sensor/solenoid etc such as the TPS and pull codes and see if the system worked as it should for if it did you would get the error code for the TPS (two of them actually).

No, it's not a jump. I speak from experience. If the car is in limp mode, and the CEL bulb illuminates with the key on, and you jumper the check connector properly and retrieve no codes, check the MOP. if it tests out of range, open the ECU and look at the MP4501 motor driver. If the stepper motor in the MOP shorted, this driver will be smoked along with a couple of resistors and maybe some other goodies.