So My max just broke down. Just got home from towing it but it did something real weird. I was driving and there had been no signs of stalling, bucking, nothing at all, just driving fine like it has been for bout a year now after my vq35 swap. So I'm at a stop light maybe a mile form my house I shift into 1st then 2nd then 3rd and I hit the gas and nothing happens I just roll, the rpms hit 0, car shuts off all the lights on the dash come up, EXCEPT, the CEL. The car will crank fine, hard and strong, but wont turn over. I was on a hill and thought since I have a manual I can get a rolling start....still nothing. The CEL light will not come on, I hooked up a scan tool, and all I get is error, I have a spare, good, tested, ECU and I swapped the one in the car out thinking the ECU could have fryed on me...again...still nothing. I think it may be my engine harness, but I have no idea, Ive been trying to search but maybe I'm just using the wrong keywords. I have a 99 with a vq35 swap with an engine harness from a 97 and a 96 ecu. lCan anyone help point me in the right direction if not help. Thanks.

 

I would first think it's one of the crank position sensors. I've not experienced the problem but read that a bad one can lead to strong cranks with no start because it doesn't know when to start. Have you checked it to see if it's good?

Are there any other electrical problems (i.e. no headlights, windows ...)? Or does it all seem to work ok?

 

no wonder your car won't start, it confused!!

 

Both crankshaft position and reference sensors have been replaced and are less than a year old already had that problem. Funny thing is I can't pull codes. My CEL light I. has been on and the only codes I pulled were o2 sensor codes, evap, egr, and a knock sensor code that has been more than frustrating. But now when I try to pull codes it just shows error on the scan tool. And when the keys in the on position all lights but the CEL light will not come on. Which leads me to think its the harness?

 

And yeah my car is very confused but I thought this would be the best thing because now wh3n I was ready I could throw a jim wolf in it and also not have to worry about the 99 bull immobilizer problems that had already set met back

 

Oh yeah everything works fine Windows radio headlights all electrical is fine no signs of anything

 

Can you check the main power wire going to the ecu to see if you are getting voltage there?

 

I have a feeling your ECU isn't getting power. Check all your fuses, and wiring again.

 

That's what I think as well which is the power wire? i will check tommorow

 

I'll check this also..should there be a fuse specifically for the ecu?

 

I just checked all the fuses related to the ECM and they all check out fine. Inside the car and under the hood. I also check all the fuses that were battery related as well as the ones that said electrical parts.

 

So Its been nice out lately which gave me a chance to look at my car more in depth. I checked all fuses (inside and under hood of car) and all grounds which all check out okay. I checked for fuel and spark, and just like I assumed, I got neither. Car cranks good a strong but wont turn over. I did check for voltage at the ECU and got nothing. Also swapped out ECUs again with a known working condition one and still nothing. So that assumption was also correct. Andy Ideas on what it could be? At this point would it be safe to say that I have a bad Engine Harness? And if so how can I check for continuity in the power or ground wires to the ECU? Also can I somehow hook up a power wire straight to the battery too see if The car can turn over to confirm it is the wiring harness?

 

Start by lookin at your harnes to get power to your ECU....then u cna start to check somewhere else...cuz an ecu without power wiil do like that...it will crank no start....if things arent right after go further in your harness...

 

so am i just checking for any cracks? any sign of wear?

 

well...for wear yes, are your motor mounts enough stiff??....maybe the harness can be submit to hard traction if i can say....check out for poor connection too...or your computer ground!

 

No my motor mounts are not stiff they need replaced. I was just about to do that as well as rebuild my suspension. I will check for wear as well as the grounds at the computer. as far as connection goes everything looks to be fine, tight and snug in each pin.

 

Shot in the dark but did you check the eccs relay? ecu power appears to come from there to pins 67 and 72 of the ecu.

 

I checked for voltage at both of those pins but i got nothing. I am going to check again today. But I didn't see an ECCS relay under the hood or in the car. I thought it was going to be under the hood by the fusible link box but there wasn't one that said ECCS. I have a 99. Where is that relay located?

 

I'm looking at a '96 but I'm not sure it matters. The eccs relay is in the relay box near the battery. BTW, you should be checking for voltage at 67 and 72 with the ignition on (if you weren't already doing so).

Take a peek at page 106/107 of the EC section in the fsm for the flowchart and diagram.

 

whats crank sensor you used, 3.0 or 3.5. if you used 3.5 you grinned away some of the metal on the block right. Also check that the crank sensor is good not corroded. Also I'd take off the sensor and reinsert it again

 

This is what I'm working with..And I know its a relay so it wouldn't be on the inside of the car although I checked there too and its not there

 

I used the 3.0 liter oil pan and sensor

 

EGI is the relay.

BTW, if you do continuity testing from there to the ecm it would be a good idea to disconnect the battery as a precaution.

 

I was going to switch the relay with one from the rad fan to see if it will start

 

I really think its the crank sensor i had similar issue at one point of time, it was due to corrosion in the wire, Antifreeze was leaking for a bad hose right onto the connector.

 

i swapped the fuses and still nothing. My crank sensor went out to right before i did the swap. thats a brand new crank sensor from Nissan. When mine went out though I was still able to get power to the ecu and read codes from the ecu to know that that sensor was bad. I cant read any codes the cel wont come on now i have no fuel or spark. this is really frustrating. I wish i could just bring it somewhere to get rid of all these electrical problems this thing has

 

Well from what I know Crank controls, spark. So that might be a cause. Like I said check the actual harness

 

Did you ever get it fixed? Curious to know what it was. Sorry to hear you're having so many problems with the car. I wished I would have kept the VQ35 now and dropped it in mine.