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2003 Corolla Non Start

by paul2003corolla, May 21, 2010



Hello to everyone. Here is my problem: I have a 2003 toyota corolla that just one day stop cranking over. I've ran a lot of different tests, here are the things I've checked.

1. New Battery voltage=12.4 v when checked

2. Alternator checked at autozone=fine

3. Starter motor checked at autozone=fine / ran a second test bench test starter motor was good. I think the solenoid may not work, but was confirmed by autozone that is does. If solenoid is out should there still be some type of noise?

4. Changed the starter switch

5. Cleaned and checked the terminal cable running to battery and ground / good connection

6. Checked the cable from battery to starter solenoid got voltage, but when cranking over no current change.

7. Changed the fuse 100A to the starter motor.

8. Checked the yellow wire which is the alternator wire no voltage.

9. Checked the white wire which is constant 12v = fine

Could it be ecm or neutral safety switch? Please help any ideas? Any other tests I need to run? What about tach wire? There was an alarm system hooked up to the car at one point, but when battery died I could not bypass the valet due to no button on switch. Poor job done by alarm guy so I took it apart and reconnected the red wires under the dash to the ignition. The power that was being pulled from the alarm was tapped into the tach wire instead of the constant 12v maybe that could have done something to the ecm? Please anyone HELP! this has been very draining.

Bad ground, perhaps?

Given that you have done a pretty exhaustive diagnosis and run down the usually list of suspects, I would say that alarm system - or what ever is left of it, is the most likely source of the problems.

Having an aftermarket alarm poorly installed is probably the most likely cause of the issues you are seeing. Very possible that one of the lead wires to the alarm system is shorting to ground somewhere - or wiring incorrectly installed such that you have ground loops which will add excessive electrical noise. Unfortunately, you'll have to chase all those wires off the alarm system to make sure they are either completely removed or find where they were tapped off of. I've seen some alarm installs where the installed cut into the main wiring loom - that is a surefire way to cause any number of electrical issues.

Bad ground, perhaps?

I've checked all grounding seems to be good.

Given that you have done a pretty exhaustive diagnosis and run down the usually list of suspects, I would say that alarm system - or what ever is left of it, is the most likely source of the problems.

 

Having an aftermarket alarm poorly installed is probably the most likely cause of the issues you are seeing. Very possible that one of the lead wires to the alarm system is shorting to ground somewhere - or wiring incorrectly installed such that you have ground loops which will add excessive electrical noise. Unfortunately, you'll have to chase all those wires off the alarm system to make sure they are either completely removed or find where they were tapped off of. I've seen some alarm installs where the installed cut into the main wiring loom - that is a surefire way to cause any number of electrical issues.

Thanks for the replies. I think there were a few lead wires that were grounded because the installer could not find the correct wires to tap to. I think you are right about the shorting of one of the wires. A mechanic came by and hooked his ecm reader to the car and found no connections to the ecm. He's saying that it could be bad connection to ecm or ecm is dead. If it were a bad connection how would I check this? Which wires? Thanks again any thing would help.

I hope the shorted wires didn't kill the ECM - that would be a major PITA.

The diagnostic port is under the dash, just left of the steering wheel. This car follows OBD-II specs, ISO protocol. There is a link to a site that spells out the pin assignments: http://www.obdii.com/connector.html

The ECM itself is underneath the glovebox. Pretty hard to miss - as the ECM is pretty decently sized. If you have a multimeter handy, you can try buzzing out the wires yourself. Though, since the alarm job was botched in that manner - I would highly recommend pulling the battery off to prevent possible further damage from moving the wiring around in the attempt to find the short.

Fishexpo101 thanks for all the good info. Batteries been disconnected only connected for testing only. I'm gonna remove the alarm and then do my test to find if there is any shorts. I also found something really interesting, here is another reply on dead ecu that I have found (Has anyone tried this and will it work?):

Question

i have a 97 chevy cavi.2.2 auto,i have a bad ecu box,it got smashed,,i need to replace it,will a junk yard one work,,will i have to take it to get flashed,or a code of any kind.when i put it in,the car starts for like 2 seconds and shuts off???with a junk yard box,

Answer

First I would try this! It may run! And if it does or does not you should have the computer reflashed. You can have the reflash done by anyone that has a Tech 2 scanner.Turn ignition switch to RUN position. Momentarily turn ignition switch to START position. DO NOT start vehicle. Wait 10 minutes. When SECURITY indicator light changes from flashing to off, or from on to off, turn ignition switch to OFF position. Perform this process 3 times. After third time, vehicle should start on next ignition cycle.

Here is the link: http://www.justanswe...-ecu-box-it-got

For some GM cars, that is true. Unfortunately, not so easy on the Toyota ECM. Even reflashes go - the Toyota ECMs are not as flexible as other manufacturers - many Toyota boxes cannot be "reflashed" in that general sense as some parameters cannot be modified.

Kind of weird that the installer played with the lines running to the ECM. I can't think of any reason to, unless the alarm system had a remote start feature or an immobilizer feature. Those features in generally, can cause all sorts of headaches - even for a competent installer.

This reminded me of one car that I tried to fix for a collegue. In her case, someone tried to retro-fit other Toyota alarm systems into a Corolla (Toyota Highlander alarm to the Corolla) - that alarm has an engine immobilizer feature that is keyed to a chipped key. Without the key - the car will not run at all, as it kills fuel and ignition at the ECM. Installers actually taped the key to the outside of the alarm system, inside the wire loom. Once the battery dies - you can only guess what happens. Even replacing the battery was a no-go - as she already pulled the battery power, which caused alarm to go into some default fail-safe and effectively bricked the alarm system. I ended up backtracking as much of the wiring as I could - car runs, but "acts" up every once and a while.

Thanks again Fishexpo101. All the reply post was wonderful and a great learning experience. I was able to go back and trace all the wires and found out that there was a fuse a 15A to be exact under the dash which had blown out due to alarm system. So, I replace the fuse and walla it worked, but when I shut the car off it blows the fuse. I guess I have to run a few test to see where it could be. I kind of narrowed it down to be either a faulty alarm brain or the power locks. The culprit I believe from looking at the alarm install manual would probably be the power locks that only has one relay hooked up to it, when instead should have at least two because its pulling to much current for four doors. I'm going to buy more fuses so I can run a few test and hopefully adding another relay should solve the problem. Problem Fixed! Thanks a lot Fishexpo101 you've been a great source of help once again.

Great to hear!



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