2004 Quest- No Spark After Timing Chain Fix

[gijoe985]

Hello All,

Curious if someone on here, maybe Nissan tech, could help point us in the right direction. I'm a high school shop teacher. I had a student bring in his mom's Quest with a loud ticking from a broken timing chain guide. He took apart the front of the motor, never removed the chain, but he replaced the timing chain tensioner and guide. After he got it back together it would not spark. Originally I had him looking for unplugged sensors, etc, but after two days of him looking, I decided to step in and help. We went online and were able to find a 2004 Quest FSM, from there we started the diagnosis procedures. Where we stopped the other day was that we only found .5v to pins 119 and 120 going to the ECM and it is supposed to be battery voltage. As we continued through the steps we also found that we had continuity between both those pins to ground as well as to power.

We'll continue our diagnosis soon, but if anyone had any ideas of what he may have crossed/pinched, it would be greatly appreciated.

[frapjap]

Welcome to NICO!

I almost guess that there is something he isn't telling you. Maybe he didn't disconnect the battery and shorted something?
I'll try to get you some more help.

In the meantime, maybe be sure that the battery is charged fully? Were you able to confirm that all sensors were attached?
Maybe the security tripped and has locked up the ignition?

While we get you some more ideas, check out this youtube channel and try to get in touch with the user. He might have something useful for you.
https://www.youtube.com/channel/UC5NVvm ... rhD_Bealpw

[gijoe985]

I may try looking at it more tomorrow. We just went on spring break.

I had thought about the security system. Not fully aware of how this one works I looked it up and it does not appear to be the problem. From what I read a key would flash on the instrument panel.

I know that he actually dropped the battery and lost fluid. He bought new acid, filled itz and charged it. We tested it with our tester and it came out OK.

Thus far no DTCs and all sensors appear connected from a visual inspection.

Joe

[PapaSmurf2k3]

Yeah if it cranks over normally, the battery should be fine (cranking draws the most power... way more than spark).

My best guess would be that some ground somewhere got left unconnected, or maybe he damaged a cam angle or crank angle sensor during the work.

[gijoe985]

According to the service manual, all grounds seem to be good, we'll need to check the sensors, but I don't think sensors being unplugged would give us the missing voltage on pins 119 and 120 on the ECU. There may be a short there. Not sure how, but it seems logical.

[gijoe985]

So, we tested and confirmed that there is a short. From the process of elimination we know that it is related to the large white wire coming off the battery, that goes to the fuse junction box. We've started taking things off, one by one, and have yet to figure out where the short is specifically. I've got the student messing with wires while I scan through the wiring diagrams.

[PapaSmurf2k3]

Yikes. Is it drawings any power? How many milliamps do you see if you hook a meter up inline with the battery?

[gijoe985]

We didn't test (should have) just used a dummy light and unplugged things until it turned off...

[gijoe985]

OK- So I took for granted information from my students. After I checked the engine for DTC codes, the code reader was not able to communicate with the engine. So... what wire/fuse should I be checking?

[PapaSmurf2k3]

If its not able to communicate, its either the data link connector cable, or the ECM that's fried I would think.

[gijoe985]

How about a fuse? Or even a shorted power cable. If the ecm doesn't get power, it won't communicate... Gotta love electrical. This student is learning why electrical diagnosis technicians get paid well...

[PapaSmurf2k3]

The ECU isn't getting power?
If that's the case, look at the wiring diagram in the FSM and see which ones are giving it power and ground, and check them out.

[gijoe985]

I think this is back to where we were earlier. The trouble shooting steps had us check for power on terminals 119&120 on the ecm with key on. Instead of battery voltage we got .5v. Later on we found that we had continuity between those pins and ground as well as power. So they much be shorted out. Where is the question. Hard to tell... I wonder if he crossed something at point A and created a short at point B by burning through some wires... We shall see...

[PapaSmurf2k3]

Sounds like one should be power, the other should be ground. Maybe check for continuity between each of them and ground. If you know which one is supposed to be power, maybe you could just run a jumper wire directly to that pin?

[frapjap]

This sounds just like an issue I recently had with my Subaru. Everything was getting power and tested well, but the ecu was toast. Pop that bad boy open and look for any obvious problems.

With any luck, your student will get to purchase a new ecu due to shorting whatever he shorted and learn how to program it into the chassis with Tech 2.