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86-95 Trucks & 4Runners 2nd/3rd gen pickups, and 1st/2nd gen 4Runners with IFS

when to replace ecm?

Old 07-12-2019, 04:24 PM
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when to replace ecm?

so i tested all the ECM Wiring Connectors Voltages outlined in the fsm. i get voltage everywhere except stop light switch (they didn't work before).the truck will run for a second or two and then die if tps and vafm is plugged in. If they are both unplugged the truck runs fine and once plugged in engine dies. is their anything else to test if before i replace ecm? i tested the vafm resistance and just about everything outlined in the picture:
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Old 07-12-2019, 05:32 PM
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What vehicle are you working on (year, engine)?

Are you saying that the Brake (stop) lights don't work?

Bad ECUs are not that common on Toyotas, so I do my best to diagnose problems before swapping out ECUs.

It from my older 1987 22R-E EFI diagrams, it looks like the STP is an input to the computer. The brake lights need to be on (or at least the brake light switch on the brake pedal needs to be closed) for the voltage test to work.

If you are stepping on the brake and not getting voltage there, you likely have a problem in the brake (stop) lamp wiring.

Do you have a jumper wire connecting the FP and +B terminals in the diagnostic box? The engine should not run if the VAFM is unplugged and you do not have a jumper in the diagnostic box.

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Old 07-12-2019, 05:44 PM
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engine 3vze 1994
brake lights don't work but i am not too worried about that one yet.
no jumper wire in diagnostic box and engine runs fine without tps or vafm plugged in. but will not continuously run with either plugged in. it just starts for 2 seconds or so then dies.

Last edited by mike250; 07-12-2019 at 05:46 PM.
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