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Resetting the Computer


elbpf
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I completely rebuilt my engine (VG30E) and I have it all back together, but it idles high and it sounds like I have some valve tapping on the drivers side. I hate to run it too long, but I did get it warmed up enough to pull the following codes from the ecu:

 

11 - Crank Angle Sensor Circuit

21 - Ignition Signal Missing in Primary Coil

43 - Throttle Sensor Circuit

 

The Crank angle sensor (as I understand it) is built into the Distributor which I bought brand new from Nissan, and also have a new Throttle Position Sensor. My Idle Air Control Valve was bad so I replaced that as well with a working part (10 ohms). I have also set the timing with a timing light. None of which has really made any difference at all. Other then the valve tapping and the high idle the engine sounds great.

 

I have read that sometimes the computer needs to be reset, but I am not sure if this is true for my engine. I am also not sure if I possibly need a new ECU, or if there is something still off with my timing (considering the valve tap).

 

Any info or insights on this would be greatly appreciated, thanks.

 

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Unless there's a more comprehensive "flash" that a dealership would/could do, as far as I know all you have to do is disconnect the battery and wait a few. To speed things up you can touch the + and - cable ends together (AFTER removing BOTH from the battery - just the loose cable ends). The computer will then have to "re-learn" when you fire it back up and let it idle.

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Yes, completely disconnect the battery and then turn the ignition on and step on the brakes or turn on the lights or something to drain any 'residual' voltage. Then I'd give it 5 minutes and hook it back up. That way you can run the engine again while it is still warm to minimize run time. It might be a good idea to drive it around the block to help the computer relearn in real driving situations.

 

A couple of Q's, how did you set the timing with the idle high? The ignition timing is supposed to be set at 750-800 rpm idle.

Have you checked the output of the TPS to make sure it is adjusted correctly? Mine has a poor connection and it will idle high until I physically wiggle the connector, then it will drop to normal.

do you have a copy of the Factory Service Manual? There is an entire proceedure starting in EC, page 24; kinda too much to repeat. You can download a copy of the FSM from the pinned thread in the Garage section.

 

B

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The idle never did actually come down to the normal speed, so I did set it while it was idling high, partly hoping that might be bring it down. I bought a new TPS and if I remember correctly the ohms only go down to about .65 or so (before the rebuild I was able to get it down to zero).

 

Based on the error codes I am getting and the fact that I can't set my TPS down to zero anymore leads me to believe that I have my timing belt off by a tooth or two. Not sure if that would cause all those errors though. I also double checked the belt three and four times to make sure I had it in correct, but I guess I could had some of the marks off.

I have a friend that works at Delta and he has access to some factory type manuals/guides, but I will download the one you mentioned to see if it is any different.
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It is the FSM that Nissan provides to the factory techs and should have all the information you need, including trouble shooting proceedures and specs.

Divide and conquer. I'd make sure the TPS is set properly and outputting the right range first and see what that does to the idle. The TPS is unrelated to the timing belt and having a tooth off may be what is making one side noisey, but I would think that would make it idle lower, not higher.

 

Yes, download it and follow the proceedure, that is what I would do...

 

B

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So, I have done a little more research on this and I have found that there is a ground wire that attaches to all of the components that I am getting errors for. I have gone through the diagrams on the FSM (thank you very much for directing me to that, very helpful), and I have found some diagrams that show a ground wire, but I am having a hard time locating exactly where that ground cable is.

 

I have a ground cable (small metal mesh cable) that is currently attached to the passenger side fender and is broken, hanging, and I don't know where it goes. I was wondering if this might be the one I need, and if someone has a picture of theirs that they could post, so I could see where it goes, I would greatly appreciate it.

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Good sleuthing, I had not heard of that. The ground wire you describe normally goes to one of the blots hogding the heat shield on the manifold IIRC. That was a long time ago and I have headers now so I can't confirm 100%.

 

I'm wondering if the ground isn't to the ECU like MAF sensor does which is why you can't locate it?

Read this, and maybe that item will help... :shrug:

(I'm not good with electrical)

http://www.nissanpathfinders.net/forum/topic/36667-bad-maf-harness-ground-nissan-official-fix/

 

B

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So, I finally found the problem. It was the Throttle Position Sensor causing the high idle speeds. Turns out I had to unbolt the TPS so I could freely spin it past the position that the bolts would allow it to go. Then I started the engine and actually turned the TPS until it read 0 ohms. Apparently this allows the ECU to reprogram the TPS so you can turn it back to the position for the bolts to hold it and still maintain the 0 ohms at idle.

 

Once I did that and got the idle speed back to normal, I could then set the timing with the timing light. The engine runs great now so I assume I got the timing belt installed correctly and the ECU is still reading code 55 after three or four full test drives.

 

Thank you all for your input on this.

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