Mil light, but no error codes
Discussion
Yes, I have had the airfilter box off, the sensor is reconnected so the problem isn´t there. If I disconnect the airtemp sensor (the sensor on airfilter box) the computer gives a faultcode on the airtemp sensor.
I might have reset the faultcodes and not the adaptive maps.
Is it possible to get this scenario if the AFR has been outside the limits and is within the limits when the computer is hooked up to the ECU?
I might have reset the faultcodes and not the adaptive maps.
Is it possible to get this scenario if the AFR has been outside the limits and is within the limits when the computer is hooked up to the ECU?
Is it possible that there is a short to earth on the ground side of the MIL light its self that is making it illuminate.
I think (though may be wrong) that the ECU illuminates the light by earthing a single wire connected to one side of it with the other side held at +ve. A short to earth on that side betweeen the light and the ECU would cause the light to come on without the ECU being involved.
I think (though may be wrong) that the ECU illuminates the light by earthing a single wire connected to one side of it with the other side held at +ve. A short to earth on that side betweeen the light and the ECU would cause the light to come on without the ECU being involved.
Well you are in a bit of trouble as the MIL is sitting on a line driver IC chip. From the circuit I have traced the processor tells the line driver chip to go high and thats what comes out of the 14 to set the buzzer/mil light on. Therefore if you sample pin 14 you will have 12v on it.
I think it likely the other end of the mil light is to earth. biker has the circuit of the mil light somewhere on his site.
This is trouble because the pin from the processor to the line driver to tell that pin to go high is pulled weakly to earth and therefore must be being put high by the processor in order for the line driver to fire and the pin to go high.
In other words I would look again at the diagnostics cos if everything is actually negative then you may have a fault with the ecu. Check pin 14 is high when your car is running.
I think it likely the other end of the mil light is to earth. biker has the circuit of the mil light somewhere on his site.
This is trouble because the pin from the processor to the line driver to tell that pin to go high is pulled weakly to earth and therefore must be being put high by the processor in order for the line driver to fire and the pin to go high.
In other words I would look again at the diagnostics cos if everything is actually negative then you may have a fault with the ecu. Check pin 14 is high when your car is running.
julian64 said:
Well you are in a bit of trouble as the MIL is sitting on a line driver IC chip. From the circuit I have traced the processor tells the line driver chip to go high and thats what comes out of the 14 to set the buzzer/mil light on. Therefore if you sample pin 14 you will have 12v on it.
I think it likely the other end of the mil light is to earth. biker has the circuit of the mil light somewhere on his site.
This is trouble because the pin from the processor to the line driver to tell that pin to go high is pulled weakly to earth and therefore must be being put high by the processor in order for the line driver to fire and the pin to go high.
In other words I would look again at the diagnostics cos if everything is actually negative then you may have a fault with the ecu. Check pin 14 is high when your car is running.
Hi Julian !I think it likely the other end of the mil light is to earth. biker has the circuit of the mil light somewhere on his site.
This is trouble because the pin from the processor to the line driver to tell that pin to go high is pulled weakly to earth and therefore must be being put high by the processor in order for the line driver to fire and the pin to go high.
In other words I would look again at the diagnostics cos if everything is actually negative then you may have a fault with the ecu. Check pin 14 is high when your car is running.
Thanks for all information.
I´m going to check if I can find the diagrams on Bykers homepage.
julian64 said:
No, I think its the other way around. The ECU is providing a line drive chip for the positive, and the car end of the light is earthed.
You are far more likeley to be right than me.Bersides thinking about it, it would be lousy design to have the whole run to the light live all the time.
Tanguero said:
julian64 said:
No, I think its the other way around. The ECU is providing a line drive chip for the positive, and the car end of the light is earthed.
You are far more likeley to be right than me.Bersides thinking about it, it would be lousy design to have the whole run to the light live all the time.
kojak said:
Big fuse problems can make it come on, but not sure whether that would show on the laptop.
Yippee !Got a fault code reading today. It is a bat fault so it might be the big fuse, which seems a lot easier to fix than some problems in the dashboard PCB or the ECU.
I´m going to change big fuse and check through the alternator during the weekend. Think I will check that the feeds and groundings to the engine is in good shape too.
Peppe
Problem solved yesterday
I changed big fuse but that didn´t help.
Had the alternator out for inspection and cleaned all connections inside it. Seems as something had a bad connection in the alternator, since everything works OK after that I put the alternator back in again.
The strange thing is that the battery warning light didn´t come on, maybe that was caused by the same problem as the voltage spikes that triggered the ECU to switch on the mil light. The software didn´t logg battery fault all times if I was reseting the fault codes. So it seems as I had some luck when I got the fault code reading on thursday evening.
The readings of the voltage is much calmer now on the ECU software, before it was a bit noisy, jumping up and down about 0.5- 1.0 volts. Have steady readings at 13.9 to 14.0 volts now. The voltage drop from the alternator output too the battery is as low as 0.01-0.02 volts which must be very good.
Now it´s just too wait for the sun to come out, so me and Cerbie can go out for a spin 
Peppe
I changed big fuse but that didn´t help. Had the alternator out for inspection and cleaned all connections inside it. Seems as something had a bad connection in the alternator, since everything works OK after that I put the alternator back in again. The strange thing is that the battery warning light didn´t come on, maybe that was caused by the same problem as the voltage spikes that triggered the ECU to switch on the mil light. The software didn´t logg battery fault all times if I was reseting the fault codes. So it seems as I had some luck when I got the fault code reading on thursday evening. The readings of the voltage is much calmer now on the ECU software, before it was a bit noisy, jumping up and down about 0.5- 1.0 volts. Have steady readings at 13.9 to 14.0 volts now. The voltage drop from the alternator output too the battery is as low as 0.01-0.02 volts which must be very good. Now it´s just too wait for the sun to come out, so me and Cerbie can go out for a spin Peppe
Hi !
After checking the alternator and not found any faults on it, I started to change all pluswires between the alternator and the battery, including the bigfuse and the holder for it. The car worked for a week and the problem was there again.
The final solution was to sell the car, just joking
, no it was the ground wire that goes from the grounding point on the chassis below the battery to the grounding point under the dashboard. This wire was routed on the lower chassis rail very close to the exhaust and cats so it wasn´t in a good shape. I have put in a new wire that is routed underneath the coolant tank and in to the car the same way as the positive wire is from the battery into the car and the car has worked fine since then, so now I plan to keep the car forever.
Yes the ECU cancels the MIL light by itself, when you don´t have a problem with the engine.
Have you had a computer connected to the ECU and checked for error codes ?
After checking the alternator and not found any faults on it, I started to change all pluswires between the alternator and the battery, including the bigfuse and the holder for it. The car worked for a week and the problem was there again.
The final solution was to sell the car, just joking
, no it was the ground wire that goes from the grounding point on the chassis below the battery to the grounding point under the dashboard. This wire was routed on the lower chassis rail very close to the exhaust and cats so it wasn´t in a good shape. I have put in a new wire that is routed underneath the coolant tank and in to the car the same way as the positive wire is from the battery into the car and the car has worked fine since then, so now I plan to keep the car forever.Yes the ECU cancels the MIL light by itself, when you don´t have a problem with the engine.
Have you had a computer connected to the ECU and checked for error codes ?
Edited by Peppe on Wednesday 25th June 05:35
Edited by Peppe on Wednesday 25th June 05:37
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