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
Registered User
Thread Starter
Join Date: Feb 2014
Posts: 16
Received 0 Likes on 0 Posts
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:
mike250 is offline  
Old 07-12-2019, 05:32 PM
Registered User
old87yota's Avatar
Join Date: Jun 2013
Location: Portland, Oregon, USA
Posts: 2,117
Received 138 Likes on 128 Posts
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.

old87yota is offline  
Old 07-12-2019, 05:44 PM
Registered User
Thread Starter
Join Date: Feb 2014
Posts: 16
Received 0 Likes on 0 Posts
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.
mike250 is offline  
Related Topics
Thread Starter
Last Post
86-95 Trucks & 4Runners
08-07-2008 05:23 PM
Steve 1stgen
86-95 Trucks & 4Runners
05-15-2008 08:23 PM
86-95 Trucks & 4Runners
04-14-2008 02:55 PM
Michigan Mud Farmer
86-95 Trucks & 4Runners
03-07-2008 05:19 PM

Thread Tools
Search this Thread
Quick Reply: when to replace ecm?

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.
  • Ask a Question
    Get answers from community experts
Question Title:
Your question will be posted in: