Toyota MR2 Message Board - View Single Post

CJMR2T · 10-31-2009, 10:36 AM

Ok well before we worry about testing the igniter, we have another issue to worry about... That is why the MIL (check engine light) doesn't come on when you turn the key on. The MIL should ALWAYS come on for a few seconds when the key is first turned on. If its not turning on, then there is a problem either in the ECU or the ECU is not powering up.

First thing is check to make sure that your EFI fuse is not blown for some reason. If it is, then replace it and see what happens. (side note: I've seen fuses that looked fine but were blown so check the fuse with for continuity just to play it safe.

If the fuse is good, then your going to need to start checking a few signals at the ECU so your going to need a pin out of the ecu and volt meter.

1) check terminal E1, E01 and E02 for continuity with chassis ground. You should have continuity between all 3 of them with chassis ground. If not then you have a ground wiring issue.

If all have good ground, then

2) check for 12v at the BATT signal (if not present, then you have a wiring issue in the BATT supply, either wiring or this going back to the above with the EFI fuse being bad)

If you have 12v then

3) turn the key all the way on and check for 12v at +B and +B1. If no voltage to either, then we go back to either the EFI main relay or the wiring..

If all these items check out as they should, then you have all that is needed to power up the ECU and thus the problem is most likely in the ECU and you probably need a new unit.

If the above happens to be the case, before you get another ECU, fine someone that will let you test your ECU in thier car. Dont use thier's in yours just yet you could fry thier ECU in doing so if you have a problem else where that cause the ECU to fry. The ECU will not fry something else so its safer to test a suspect bad unit in a good running car to see if it'll run. If it does work in someone else's car then there is something else that is shutting down the ECU and I'll have to look into it more as to what could cause it. If it doesn't work in another car, then its deffinitly fried. This is the hard part now, if it is fried, did it just go out on its own or is there a problem on the your car that fried it???

Before we worry about that, let first find out if its bad or not....

10-31-2009, 10:36 AM	#10 (permalink)
CJMR2T Fabricator Join Date: Oct 2009 Location: Lakeland, FL Posts: 3,687 Thanks: 3 Thanked 355 Times in 336 Posts iTrader Rating: (4/100% )	Ok well before we worry about testing the igniter, we have another issue to worry about... That is why the MIL (check engine light) doesn't come on when you turn the key on. The MIL should ALWAYS come on for a few seconds when the key is first turned on. If its not turning on, then there is a problem either in the ECU or the ECU is not powering up. First thing is check to make sure that your EFI fuse is not blown for some reason. If it is, then replace it and see what happens. (side note: I've seen fuses that looked fine but were blown so check the fuse with for continuity just to play it safe. If the fuse is good, then your going to need to start checking a few signals at the ECU so your going to need a pin out of the ecu and volt meter. 1) check terminal E1, E01 and E02 for continuity with chassis ground. You should have continuity between all 3 of them with chassis ground. If not then you have a ground wiring issue. If all have good ground, then 2) check for 12v at the BATT signal (if not present, then you have a wiring issue in the BATT supply, either wiring or this going back to the above with the EFI fuse being bad) If you have 12v then 3) turn the key all the way on and check for 12v at +B and +B1. If no voltage to either, then we go back to either the EFI main relay or the wiring.. If all these items check out as they should, then you have all that is needed to power up the ECU and thus the problem is most likely in the ECU and you probably need a new unit. If the above happens to be the case, before you get another ECU, fine someone that will let you test your ECU in thier car. Dont use thier's in yours just yet you could fry thier ECU in doing so if you have a problem else where that cause the ECU to fry. The ECU will not fry something else so its safer to test a suspect bad unit in a good running car to see if it'll run. If it does work in someone else's car then there is something else that is shutting down the ECU and I'll have to look into it more as to what could cause it. If it doesn't work in another car, then its deffinitly fried. This is the hard part now, if it is fried, did it just go out on its own or is there a problem on the your car that fried it??? Before we worry about that, let first find out if its bad or not....