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Doug
Doug, ASE Certified Technician
Category: Mitsubishi
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Experience:  Mitsubishi employed and Factory trained ASE certified technician
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mitsubishi galant: i test the crank sensor..2.4L..swap..firing

Resolved Question:

how do i test the crank sensor on a 99 2.4L sohc mitsubishi galant? my problem is i'm only getting spark to one of the coils,but when i swap the coils the one thats not firing now works and vice versa.





l
Submitted: 4 years ago.
Category: Mitsubishi
Expert:  Doug replied 4 years ago.
Chat Conversation Started
Doug C :

Hi,
The crank sensor can not cause this condition. The signal from the crank sensor is used identically for both banks of coils; if it fails, neither coil will work.

Doug C :

The way the ignition system works on this vehicle is very simple, but also rather expensive unfortunately.

Doug C :

The ignition coild both receive power from the same wiring, and are grounded through the same wiring, making it very easy to determine them to be fine, since one bank always works.

Doug C :

The fire signal being sent to the coils is the only part of the ignition system that is separated; this is a direct line from each coil to the power transistor for each coil, located inside the PCM.

Doug C :

If you are having a failure on one bank only, regardless of swapping coils, you have eithe ra fault in the wiring between that coil and the PCM (highly unlikely) or a burnt out power transistor int he PCM (extremely common).

Doug C :

This typically occurs when a coil is on the brink of failing, burning out the transistor... this can happen from an excess draw from the coil (typically goes hand in hand with incorrect/faulty plug(s) on that coil), or a internal short on that coil.

Doug C :

The repair unfortunately is to replace the PCM. The PCM is located on the firewall behind the glovebox inside the car. Once replaced the ignition keys must be programmed to the new PCM or the vehicle will be immobilized.

Doug C :

Here is a diagram to help visualize how the wiring is laid out and where your potential issues are:

Full Size Image

Doug C :

Disregard the red line at the top, it does not apply to your scenario....

Doug C :

The green areas are determined OK, yellow is questionable (depending on which side is failed) and the red is your most probably failure (the transistors at the bottom)

Customer :

damn it goes that deep..the key looks like a regular key,not a transponder key.its just flat metal...

Doug C :

Ok, if you have the oval type key that says 'mitsubishi' on it, then you will not have immobilizer on your car

Doug C :

or if it has been replaced with a solid metal

Doug C :

If it is shield shaped with a star on it, then it is immobilizer based (99 was first year for that platform, not all got it)

Doug C :

If you are handy with a multimeter, you can actually check those wires where they exit the PCM for voltage while cranking; you will need to see a pulsing voltage (I will check the spec in a moment, its very little though). If there is no voltage pulsed, you have confirmed the transistor is failed

Customer :

so in other words one of the coils failed or is on its way out and it took out the pcm. so i guess i need to do a resistance test on each coil to determine the bad one,replace it then the pcm and i should be ok.

Doug C :

This would be a good idea. I have seen these PCMs fail for what appears to be no reason, however at least half of the time there is a failing/aftermarket coil on the dead bank.... or an out of spec spark plug (Bosch+4 type plugs, etc)

Doug C :

If you want to check the coils, check between terminals 1 and 2 and 2 and 3, you should see 15-20k ohms

Doug C :

When you do this, you will need to have a AA battery or similar (about 1.5V) connected on the 2-3 terminals, meter leads on the 1-2 terminals

Customer :

i'll check for a broken wire first(i highly doubt it) before i go for the pcm,coils and new plugs and wires..i have the haynes book to test the coils and everything else,buy those books give you enough info to get in trouble but they dont tell you how to get out of it!!hahaha

Customer :

thanks for your help doug

Doug C :

You're welcome. It sounds like you are pretty handy, I'd go ahead and verify that voltage output at the PCM to be sure, but this is pretty common

Doug C :

And as you saw in the diagram.... there isn't much that can cause it

Doug C :

I'm still looking for the spec for that signal, they don't make it easy to find... it's going to be around 300mv-3V max (typically about 300mv), I'd just like to get the exact # XXXXX they do change from year to year with PCm changes

Customer :

well im satisfied,no use looking for the parts today though,everyone around here is closed.if i have any more problems how do i get back to you?

Doug C :

Got it, 300mv-3V while cranking/running

Customer :

awesome,thanks

Doug C :

You can reach me right at this page any time in the future. I will receive an email when you have posted, and will get back to you as soon as I am at work and available

Doug C :

Also, your vehicle is an automatic correct?

Customer :

yes

Doug C :

Ok great... just wanted to make sure as the transistor signal pin out is different on manual trans (I posted the automatic)

Customer :

have a good weekend bro,knock a few back!!;-)

Doug C :

Thanks you too!





Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 6681
Experience: Mitsubishi employed and Factory trained ASE certified technician
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