Resolved 1G ECU bad or MPI relay? No crank no start

[Oilers199099]

Hello
I replaced my ecu and i am not getting a CEL light for 5 seconds. There is a one click when I try to turn the key behind the ecu. What can it be and where should I start. Any help will be grateful

You must be logged in to view this image or video.

I sent a spare ecu to ECMTuning this week. My other ecu was sent to foreign auto for repair but when I received it no check engine light at start up.

 

[92AWDHX40]

Take the ecu out and inspect it. https://www.dsmtuners.com/threads/how-to-diagnose-a-no-start.217951/

 

[steve]

Do you have and know how to use a multimeter?
If so you can diagnose it more. https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/

 

[Oilers199099]

Do you have and know how to use a multimeter?
If so you can diagnose it more. https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/

Hello
Ok thanks I’ll try to learn how to use one and try it out.

 

[Oilers199099]

You must be logged in to view this image or video.

I am getting the ecu rebuilt why would the relay box click. It is because the ecu is bad and not providing power to the mfi relay there? Just curious so I can learn what’s happening. Thanks

 

[arodgst]

I recently had this issue on my Laser, I switched ecu to a known good one, problem persisted, I replaced the mpi relay with a known good one, problem persisted, I switched out my starter to a brand new one and it only got worse over time. After a few weeks of not turning on the car my battery decided to not hold a charge anymore and after I put in a brand new battery the issue has gone away. I did jump start the car with jumper cables the first time and jump starting it turned it on right away. Look into your battery its probably on its way out. My issue was a low voltage problem, had just enough juice to start the car clicking away most times.

 

[steve]

I'm not sure what we are listening to in your video.
Are you just turning the ignition on and off or are you turning it all the way to start?

 

[Oilers199099]

I'm not sure what we are listening to in your video.
Are you just turning the ignition on and off or are you turning it all the way to start?

Hi
I was turning the ignition on and off all the way to the start position. It just clicks in the mpi relay box. I sent my ecu to foreign auto and they said it was rebuilt. But I don’t get a cel engine light for 5 seconds when I turn the key to the on position. The car doesn’t turn over. I still have to try the test you recommended.

 

[arodgst]

Have you tried replacing your car battery? If you can't do that try jumping it with another car with some jumper cables and see if that works, then youll know its the battery.

 

[97egl]

You may want to check the positive battery terminal where the wires bolt to the terminal. There are 3 different flat pieces of metal that are the ends of the important feed wires. They can corrode and you get connection on some but not others which can cause all sort of weird issues since parts of the car have power and other parts don't or are getting low voltage

 

[Oilers199099]

Have you tried replacing your car battery? If you can't do that try jumping it with another car with some jumper cables and see if that works, then youll know its the battery.

Ok I’ll try that I am waiting for both my computers to come back next week. Appreciate the advice. I can’t wait to drive it again

 

[steve]

I'd guess there are several issues.

For the basic check of the ECU you only want to turn the key to the Run position and wait to see if the CEL turns on, then off.

The video noise sounds like a starter circuit issue. If the starter is working correctly it doesn't even need an ECU installed to get the engine to spin over, clearly it won't start without it, but it should crank.

Yours sounds like either the battery voltage is too low or your starter solenoid is bad. It's too loud to just be an issue with the Clutch Safety Switch (assuming this is a manual car) tripping the starter relay but it's easy to check that. Again a multimeter is a valuable tool here to diagnose what's going on.

 

[Oilers199099]

I'd guess there are several issues.

For the basic check of the ECU you only want to turn the key to the Run position and wait to see if the CEL turns on, then off.

The video noise sounds like a starter circuit issue. If the starter is working correctly it doesn't even need an ECU installed to get the engine to spin over, clearly it won't start without it, but it should crank.

Yours sounds like either the battery voltage is too low or your starter solenoid is bad. It's too loud to just be an issue with the Clutch Safety Switch (assuming this is a manual car) tripping the starter relay but it's easy to check that. Again a multimeter is a valuable tool here to diagnose what's going on.

Ok that’s good to know I can try to turn the car over without the ecu. I’ll check all the wiring tracing it back to the starter. I installed a new starter with the new solenoid on it. Thanks for your advice.

 

[Oilers199099]

I'm not sure what we are listening to in your video.
Are you just turning the ignition on and off or are you turning it all the way to start?

Hi Steve

The car is turning over now. It was a bad wire to the starter. I got my ecu back still no cel light. I am not sure if they fixed it correctly. Do I remove the ecu and test the voltage at pin 103 like you said in your post? I am waiting for my other ecu from ecmtuning to come as well. Thank for your help so far.

 

[steve]

I've tried to make this as clear as I could, let me know what parts aren't.

https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/

I'm guessing (with no justification) that your ECU isn't grounding pin 63 to cause the MPI relay to activate.

 

[Oilers199099]

I've tried to make this as clear as I could, let me know what parts aren't.

https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/

I'm guessing (with no justification) that your ECU isn't grounding pin 63 to cause the MPI relay to activate.

Hi Steve

The explanations are perfect. I just have to learn to test it. I did the ohm test on the fuses which was 0. So they are all good. I’ll try the diagram test on the mpi relay and ecu. All my other lights work inside so I assumed the light bulb was out.

When you mean check for voltage on pin 103 is that on the harness side pin or the ecu pin. Sorry I am new to this and learning.

 

[steve]

When you mean check for voltage on pin 103 is that on the harness side pin or the ecu pin. Sorry I am new to this and learning.

In that case Pin 103 is at the ECU and is the unswitched backup power to the ECU. It's also used to retain the radio settings.

I'd assuming unless I say otherwise that the harness is plugged into the ECU.

In this case the voltage comes from the battery not the ECU so it you measure on the harness side when disconnected you see battery voltage and from the ECU side you'll get nothing cause they aren't connected.

 

[Oilers199099]

In that case Pin 103 is at the ECU and is the unswitched backup power to the ECU. It's also used to retain the radio settings.

I'd assuming unless I say otherwise that the harness is plugged into the ECU.

In this case the voltage comes from the battery not the ECU so it you measure on the harness side when disconnected you see battery voltage and from the ECU side you'll get nothing cause they aren't connected.

Ok Steve I appreciate all the help. I’ll start testing this weekend and see what I come up with.

 

[Oilers199099]

In that case Pin 103 is at the ECU and is the unswitched backup power to the ECU. It's also used to retain the radio settings.

I'd assuming unless I say otherwise that the harness is plugged into the ECU.

In this case the voltage comes from the battery not the ECU so it you measure on the harness side when disconnected you see battery voltage and from the ECU side you'll get nothing cause they aren't connected.

Hi steve

I got my ecu back from ecu tuning still no cel light.

I check pin 103 on the harness and get 12 volts. Pin 10 on the mpi harness I get voltage as well.

Pin 102 I don’t get voltage when it’s in the on position. Pin 107 it shows an ohm reading of 3.83 still not sure if I am doing it right.

Should I ground pin 8 on the mpi and check voltage at pin 4 and 5 according to your chart.
I checked the bulb and it’s fine as well. Thanks again for your information it’s helped a lot.

I've tried to make this as clear as I could, let me know what parts aren't.

https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/

I'm guessing (with no justification) that your ECU isn't grounding pin 63 to cause the MPI relay to activate.

 

[steve]

ECMTuning doesn't usually send back ECU that don't work.

I'm not sure what you trying to do with pin 107, it's tied to pin 102. I typically wouldn't measure resistance (ohms) on it but if I did I would also say the resistance is between these two points like 107 and ground.

MPI pins 4 and 5 are also tied together and to ECU Pins 102/107 so unless you have a short or cut wires they should all agree. What voltage do you see on pin 8 of the MPI relay?

 

[Oilers199099]

Hi Steve I get this reading for pin 8 on the relay

You must be logged in to view this image or video.

Pin 103 and pin 10 on the relay 12 volts

You must be logged in to view this image or video.

You must be logged in to view this image or video.

Pin 110
Ignition has voltage on the ON Position

You must be logged in to view this image or video.

 

[steve]

Disconnect the MPI relay and measure the resistance across pins 8 and 10 with the red lead on pin 10. There is a diode in series with the coil here so one direction will have a relatively low resistance and the other direction a very high one.

While your at it measure the resistance of the harness on the Black/blue wire from pin 8 on the MPI to Pins 63 and 66 at the ECU. You should have continuity (close to 0 ohms) between the two.

 

[Oilers199099]

Ok Steve I’ll try that first thing in the morning. If I can compensate you for your time in relying I will let me know. I never had this issue since I had the car since 1999

 

[Oilers199099]

Hi Steve

Pin 10 I don’t get a reading it’s zero
Pin 8 is .80
Pin 8 to pin 63 .80
Pin 8 to pin 66 .80

Does that sound right. Thanks

 

[steve]

Hi Steve

Pin 10 I don’t get a reading it’s zero
Pin 8 is .80

Not sure what these measurement are? Zero ohms is a short, the two points are connected with no resistance between them. Zero volts is no voltage difference between the two points.

With your meter double check what it reads with the probes apart and touching. If you have multiple resistance settings you can select use the lowest setting (ohms < kohms< mohms)