Crank No Start PURGATORY

So I drove this car home with a bit of a misfire, then cleaned up the throttle body plate and replaced the battery. That is when I got a crank no start issue. I got codes and it came up as p0335. So naturally I replaced the crankshaft sensor and the issue remained with the same code. I then tested the sensor by backprobing and I confirmed getting 5volts every time metal came near it. I thought it might be a bent trigger place so I replaced that. Still the same thing. I then checked timing and it was spot on.

Frustrated I took it to a shop, they thought it was a sensor too so they replaced the CPS too. Then when they realized it wasn’t they traced the signal back to the ECU and couldn’t figure out why the ECU wasn’t reading the CPS signal so they replaced the ECU and still NO START.

The only thing I can think of is that the battery terminals were pretty corroded when I put the new battery in it. The shop says they are trying to find the break in communication on the Data Bus and going through the wiring diagram. They have had my car for a month. Can anyone help?

New mechanic. One needs to figure out if it cranks whether it is a fuel or ignition problem, step 1.

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after a month, step 1 is the new mechanic.

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If the computer doesn’t see a crank sensor signal, the fuel pump won’t run and the injectors won’t operate.

And in some cases, the ignition system won’t function.

This is going to be a tough one.

Tester

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Why did you replace battery ?
Did you accidently hook it up backwards and blow a fuse or fusible link ?

The battery was weak and corroded. It barely started the car when it was running.

I’m not opposed to a new mechanic, but if you have worked in a shop before you would know mechanics typically don’t jump at the chance of inheriting a complex electrical issue. I’m posting here to gain some insight to either tell the mechanic as a tip or get the vehicle back and figure it out on my own.

digging into the wiring diagram is key- and might be extensive (read expensive.)

I had this happen on a Chevy Van, and the code was Crankshaft Position Sensor, but the fault ended up being a 5Volt reference signal shorting to ground for the Oil Pressure Sensor. Both the CPS, the OPS, and something else (I forget which now,) shared the same 5V reference signal, and when it shorted to ground on one branch, it killed the signal to all the sensors. It took me about a week to trace all my wires and find the right ones (some of that week was spent looking at the wrong wiring diagram… That didn’t help a thing…:slight_smile: )

I’ve got a hunch that your issue is much the same.
a dedicated mechanic can find this, and without just tossing parts at it.

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