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Doug
Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 6899
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Mitsibishi montero sport xls 3.0 2wd: 2001 mitsubishi montero

Customer Question

2001 mitsubishi montero sport xls 3.0 What could if be if I'm getting spark out of only the center coil out of of 3 coils
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.
Hi,

There are a few things that could cause that behavior, varying between belt timing (physical or perceived) or component failure (PTU or ECU).

Do you have a multi meter or oscilloscope, and are you comfortable taking the front end apart if necessary for inspection?
Customer: replied 1 year ago.

Hi Doug, When we last spoke, approx february (my computer crapped out, so I have no record of our history) We'd discussed replacing the cam gear sensor, cause it was cracked. You'd said "That sounds like it" but after replacing there was no change. I just now tried testing each of the coils outputs and they work but only if I use the connector, from the wiring harness, that's for the center coil.

Expert:  Doug replied 1 year ago.
No problem.
So we know the coils are good, we just need to figure out now if they are being intentionally shut down (As is the case if there is a timing issue, be it belt alignment or sensor problem) or if there is a malfunction preventing them from operating.
What we can do here is check our operation at the PTU since you've already had the nose apart, and I'm guessing you probably checked the belt alignment at that point (I'll have to see if I can find the previous conversation, I'm not at a spot where I can search it right now).
Looking on the top of the engine you will see the PTU bolted down in the valley of the intake area. It is a roughly 4"x4"x1" box, mounted vertically, with two electrical connectors pointing straight up.
Take an oscilloscope or a test meter set to DC volts and connect one lead to battery -positive- and the other lead to one of the wires on the 3 pin connector (keeping the connector plugged in). Crank the engine and monitor the voltage reading and record it, then move to the next wire. Do all three wires on the three pin connector.
Then go to the six pin connector. Unplug the connector and connect one meter lead to battery -negative- and the other lead to pin 1 (Blue wire). Crank the engine and monitor the voltage reading/behavior and record it. Then move to pin 2 (Black/Yellow) and finally pin 3 (White).
Let me know what readings/behavior you have on each inspection and that will tell us if you are having an intentional shut down or a component failure related problem.
Customer: replied 1 year ago.

I don't have a 4x4x1" box but rather 2, 3 pin connecters, one of which is the (I think you said Crank sensor, which checked out as per your suggested test), the other is for the cam gear sensor that I just replaced, which had a mounting bracket, but the replacement doesn't so it just hangs there.The test you now suggest, sounds like it would take 2 people to perform.

Expert:  Doug replied 1 year ago.
Its definitely there, or you wouldn't have any spark. If you have the shroud over the engine you'll need to remove it.
I circled the area in this picture, with a line drawn to each of the two connectors.

http://i.imgur.com/0Hvt2Xh.jpg
Customer: replied 1 year ago.

well the 2 things you circled are a 3 pin and a 6 pin connections, the clip that was holding the 3 pin one on had broken off long ago, and now the 6 pin unit has a broken clip as I was pushing hard to get it to click in and it broke. I'll repeat 'This sounds like it takes 2 people to conduct this test

Expert:  Doug replied 1 year ago.
That certainly doesn't sound too healthy.
If the connectors are in rough shape and you can't anchor the test leads sufficiently, then you are going to need a helper. I usually stick them in there and lay the meter on the windshield but it sounds like you are going to have some special circumstances.
I am stepping out on break right now if you want to give it a shot; if you need to wait until you have a helper that is fine too of course. I'll check back in when I return (About 45 minutes).
Customer: replied 1 year ago.

I couldn't reach the battery, and crank the ignition, and see the meter at the same time. So here's what I could do; Without another set of hands/eyes, 1st; I wedged the red cable into the red/pos batt terminal, and using the black lead, each pin registers ?5 or 50? whether the ignition is on or off, on either the male or female ends of the 3 pin unit, and this is with the ignition on or off. @nd I unplugged 6 pin unit and put black wire to negative batt. term.; All but one had the gauge registering, The one that didn't register (ignition on or off is the white wire (the wire 2nd closest to dashboard.

Expert:  Doug replied 1 year ago.
Both of those tests require the engine to be rotating.
When the engine is rotating, the PCM sends low voltage pulses to the wires on the six pin connector. These in turn fire transistors that send ground pulses to the wires on the three pin connector.
We need to make this inspection because it will narrow us down considerably. If there is proper operation on both fronts, then we would suspect a wiring/connector issue between the PTU and the coils.
If there is proper voltage pulse bu no ground pulse, we would know the PTU is bad.
If there is no proper voltage pulse, then we would be narrowed down to a timing mismatch (actual or perceived), a bad PCM or wiring problem between PCM to PTU, at which point further inspections could be made.

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