AdsoYo

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The last few days the car has had this bizarre sudden death issue. A few days ago I was cruising along at 35mph, the engine died for a split second then came back and operated like nothing was wrong for the rest of the day. The next day, the same thing happened again. The third day, the engine died and stayed dead but when I turned the ignition off and back on, it started up and drove fine for the rest of the day.

Now today, it was driving fine and it did the split second death thing again and I happened to be looking at my gauges. When it cut out for that split second, the tach started whipping between 0 and 4000 ridiculously fast. Speedo was fine, the smaller gauges dipped and went back to normal (because the engine was off for a split second, I consider that normal behavior).

Then a little later the engine died and stayed dead. I was able to coast to a side street and have a look at things. The tach bounced around with key on only. I popped the hood to check connections since this seems like an electrical gremlin. With key still on I could hear the fuel pump prime on and a off a few times.

Everything I could reach seemed tight. Tried wiggling the grounds on the drivers side head and passenger fender. Tried wiggling battery terminals, MAF, PCM, coil packs, coolant temp on water pump, alternator. Couldn't reach cam or crank position sensors but I'll get there. No check engine light but I'm charging my laptop to scan.

I think the biggest clue is the tach bouncing around with key on and fuel pump cycling on and off. The lights in the car stay on when the engine dies so I still have electricity there. The engine will crank fine and about half the time it will fire and die immediately. I can get a rev in if I hit the throttle but will die right away. It depends on if fuel pressure holds or not. So far it primes every time I turn the key on but just doesn't hold. Any ideas while I dive into this thing?

AdsoYo

iTrader: (1)

well my suspicion was right. Looks like crank position sensor. hptuners is showing stored P0335 and P0336 codes (crank position sensor A circuit and crank position sensor A circuit range/performance). Car fired right up in the garage and I was able to re-park it just fine. Any idea where I should look for a solution? Is it the sensor itself or the wires? Could my 24x crank reluctor wheel somehow be misaligned? I feel like that's unlikely.

SS RRR

iTrader: (2)

I was going to say, tune that **** out, but I guess it is needed. Have you taken the sensor out to see if there's physical damage? If it isn't, start tracing wires.

AdsoYo

iTrader: (1)

I'm just gonna get a new one from the auto parts store whether the sensor is bad or not. I have spares of nearly everything so I might as well have a spare of the crank sensor as well.

I'd like to view the crank signal square wave. Can anyone recommend any software?

Slowroll

You will need a scope to watch sensor waveform, and back connector or make a jumper.

SS RRR

iTrader: (2)

I have no idea. Sorry.

Slowroll

Back probe. It will be a AC signal

AdsoYo

iTrader: (1)

I pulled the old sensor and it looks good as far as I can tell. I bought a new one anyway with a lifetime warranty for peace of mind.

I followed the troubleshooting steps in this thread for P0335: https://www.ls1gto.com/forums/showthread.php?t=201783

When measuring the 12 volt reference circuit to ground there should be at least 11.5v. I was reading 18.6v. Good to go according to these instructions.

When connecting a test lamp between the 12v reference circuit and the crank sensor signal circuit, the fuel pump should operate. I used a paper clip to short the two circuits and sure enough, the fuel pump primed. Good to go according to the instructions.

When measuring the 12v reference circuit to the low reference circuit there should be at least 11.5v. I was reading 0v. I think I found my problem.

I'm going to try and find what pin the low reference circuit connects to at the PCM and check the wire for continuity and resistance. If it's good that should leave the PCM itself. I hope that's not it, I've had a bad PCM before and that time it manifested as a P0353...

As for the oscilloscope, I found a product called PicoScope that looks like what I'm after. I still have a lot of researching to do as far as what bandwidth, sampling, and channels all mean but I'm not too worried about the scope now that I see this is most likely a wiring issue.

Slowroll

18.6v isn't right, too high for a 12v system.

AdsoYo

iTrader: (1)

what would cause that?

AdsoYo

iTrader: (1)

Apparently the diagram I found of the crank position sensor connector was backwards, or I read it backwards. That high voltage was the crank signal circuit, not the 12v circuit.

I checked all 3 wires for continuity and resistance. All 3 wires are intact and all 3 have 0.1 ohms. That's testing from the connector terminal of the sensor to the PCM, not by puncturing the wires or anything.

When I checked voltage on the 12v circuit, I was reading a solid 10.92v. Then when I checked 12v to low reference I got 10.92v again. That is lower than the 11.5v the instructions call for. Not sure where to go from here...

AdsoYo

iTrader: (1)

Also I should mention that the old sensor had no evidence of contact with the reluctor gear. With the sensor removed, I tried to move the gear back and forth with a screwdriver and it wouldn't budge so I'm considering the gear and everything in that neighborhood to be okay.

Slowroll

Condition description sound consistent with a bad crank sensor. Scanner , win aldl, you need to see what PCM input do when engine is erratic. The linked thread is a little hard to follow verses see the actual diagnostic chart.

AdsoYo

iTrader: (1)

Yep you got it. I replaced the sensor and just put 5 miles on the car with no issues. If it starts having issues again at some point, I'll post up here.