2000 LC - Crank, No Start - Immobilizer working

[inthepines]

Hey everyone,

I have been working on my new-to-me 2000 LC on and off. I bought it about 10 months ago, and found out soon after that it needed an alternator. I had some other work taking up my time, but finally finished up the alternator replacement, and got everything put back together.

At first, when attempting to start it, the security light in the center of the dash would not stop flashing. I did a lot of reading, and it seemed to be related to the immobilizer circuit.

Steps Taken:

• Checked the EFI fuse in the engine fuse box, it was melted on one side. I replaced this fuse with the radio 20A fuse (confirmed working), and tried starting it again. The security light on the dash is now turning off when inserting the key, however the truck still doesn't start.
• Read DTCs with a code reader, and it pulled P0335 (Crankshaft Position “A” Circuit Malfunction)
• Did some additional reading about this issue, and wire damage from the drive belt seems common. I checked the wiring, but I was not able to find any breaks/nicks. The wiring seems to be ran behind the fan bracket, so there is a small portion that I cannot see.
• I was able to find where the crank sensor goes back on the ECM (E7, pin 23 and 24), and I took readings with an ohmmeter at the connector. With the crank sensor plugged in, I would get about 8.5 kΩ, and with the sensor unplugged I was getting around 25 kΩ. (I find this strange and think it should be completely open...)

Ideally, I would like to take resistance readings of the crank sensor itself (at the sensor), and also continuity test the wiring from the sensor to the ECM to make sure that's all good and low resistance. I need to get some alligator clips for this, but once that is done I feel I can rule out the wiring.

It was running fine before I did the alternator job though, and I feel like the crank sensor wouldn't go bad just sitting for 8 months. I didn't go near the crank sensor when doing the alternator, and I don't think I unplugged anything other than the MAF sensor.

I wanted to post here because I'm going down this path, but there are some things I am not sure of. I read a lot about this, and it seems like in some cases the P0335 code represents with a no-start condition, and at other times the truck is running fine. I figured it would be good to get some extra ideas!

I also feel like it could be a fuel issue, and maybe I should look into the basics (fuel & spark), but the engine code points me this way.

Thanks in advance for the help!

 

[nissanh]

Do you have a wiring diagram? sorry I don't. It might lead what other connections the pins 23 and 24 are connected to. The 25 Kohm should not be present (open loop is what I would expect).

Did you also try to install a separate relay for EFI circuit inside the fuse box?

 

[inthepines]

Luckily I did find a wiring diagram here: LC100 Factory Service Manual - https://lc100e.github.io/ (Electrical Wiring Diagram > Overall Electrical Wiring Diagram > Engine Control > 2UZ-FE (1998.1 - 2000.7))

So it looks like the green wires to the cam and crank sensors ultimately splice together before returning to the ECM. This led me down a chase for that J10 junction connector, which the FSM shows as being right above the ECU, but I don't see anything there.

At this point I'm just going to see if I can test the sensor and wiring independently, and see what that gets me.

I still have trouble believing it's a coincidence that this is happening after doing the alternator job, and not something I did or missed.

 

[inthepines]

Did you also try to install a separate relay for EFI circuit inside the fuse box?

I didn’t change the relay out but with the security light operating normally (flashing until I put the key in), I figured the EFI relay and fuse were working correctly.

I may be misunderstanding how that all works, but with the EFI fuse pulled out the security light won’t stop flashing, even with the key in.

 

[inthepines]

A little update, I checked the wiring from the crankshaft sensor back to the ECM, and both wires tested good (<1 Ω).
I was able to test the sensor itself and got a similar reading as from the ECM side (8.5 kΩ), which appears to be out of spec.

I took the bolt off that holds the sensor on, but the sensor is stuck in there.

I was thinking of trying to read live data with a scan tool, to see if it shows RPM, but I'm not sure if that will work. I can't help but think it could be fuel related or still something with that EFI circuit.

 

[inthepines]

Just wanted to update this in case anyone had a similar issue. It was the Crankshaft Sensor.

There was some corrosion starting on the sensor too, so it was pretty stuck but I was able to get it out with a wood dowel and a hammer, hitting the connector lightly to rotate the sensor in place. I'm sure if the sensor was bad enough it could break by doing this, but it worked for me. I replaced the sensor and it started without any issues.

Finally out of the garage and time for some suspension!

 

[excessive]

thanks for posting for anyone else who comes across this in the future. way to stick with it and get it solved

 

[Malleus]

Just wanted to update this in case anyone had a similar issue. It was the Crankshaft Sensor.

There was some corrosion starting on the sensor too, so it was pretty stuck but I was able to get it out with a wood dowel and a hammer, hitting the connector lightly to rotate the sensor in place. I'm sure if the sensor was bad enough it could break by doing this, but it worked for me. I replaced the sensor and it started without any issues.

Finally out of the garage and time for some suspension!

Both the service manual and the EWD are in the Resources section. You should download them for future use.