This is gonna be a long post so sorry in advance!

I recently replaced my radiator, condenser, water pump, engine block flange/seal, crankshaft position sensor o-ring, thermostat housing, thermostat, and a few coolant hoses along with some other seals/gaskets while I had everything apart. I put everything back together and I'm now getting all crank but no start.

Scanned the computer with my OBD II reader and I'm getting code P0335 (Crankshaft Position Sensor) which has in-turn caused my EMS to disable spark and fuel. I also noticed that during crank, the RPM gauge sits idly at "0" which helped confirm my sensor was probably bad. Ordered a replacement sensor and installed. Same issue - Cranks all day but no start. I read somewhere that pins 2 & 3 on the sensor should have continuity but that wasn't the case. Sent the sensor back and obtained another - Still no continuity on pins 2 & 3 and all crank no start.

I obtained the engine wiring schematic and determined the following:
Pin 1 brn/gry = Signal wire to EMS pin A74
Pin 2 blk/gry = Ground wire to EMS pin ***
Pin 3 red/blu = Power source wire to F02 fuse (20AMP)

I've tested all engine bay fuses and confirmed my main engine relay is working. I've tested continuity on the blk/gry wire from the sensor plug to the EMS pin, the brn/gry wire from the sensor plug to the EMS pin, and the red/blu wire from the sensor plug to the 20AMP fuse pin. Each working with no resistance or connection issues. I also tested power to the plug by switching the ignition over to ACC and received approx. ~7.5 volts. Battery is good with a sitting output of approx. 12.5 volts.

I checked the plugs/pins on both the EMS and the 2 connector plugs - all clear and clean of any debris. I've reseated all plugs, performed an ECU reset, cleared the trouble codes and tried to start again - Same issue and the P0335 trouble code came right back.

So here I am. Engine won't start because the computer can't determine crankshaft/engine timing and now I have a power steering fluid leak to add insult to injury. At least I know my starter motor is a trooper...

Any help at all with this would be unbelievably appreciated. I've scoured all other forums/threads and tried everything that I can think of here. I really doubt that both the crankshaft sensors I got were bad and now I'm not even sure if continuity is really needed... Anyone?

 

If I'm reading the Bentley right, you should be getting 0.2 volts on pin 2, 0.1 volts on pin 1, and battery voltage at pin 3 at the sensor with the key in the on position and the engine off. All readings are to ground.

Do you have a scope to back-probe the sensor signal? That would probably tell you the most. The reluctor is a 58 tooth wheel, and the sensor looks like it should produce a square wave with a 5 V peak-to-peak amplitude and a +2.5 V offset. Otherwise, it says that pin 2 should have 2.5 V on it with the engine at idle, which makes sense because 2.5 V should be the RMS value of the square wave.

edit:

Your pinout doesn't match the Bentley. It gives pin 1 to pin 74, pin 2 to pin 55, and pin 3 to fuse F02. What I said up higher matches the pinout below.

sensor pin -> ECM pin/Fuse
1 ----> 74 is brown/gray
2 ----> 55 is black/gray
3 ----> F02 is red/blue

 

Thanks for your response - I do plan on getting a better test on the individual sensor and will try to get to that this weekend.

After checking my notes, I did get pin 1 & 2 backwards when typing this up but I have it right on my wiring sheets which I have attached. Either way, I've tested all 3 wires and all appear to be working as expected. There is also no visible damage to any of the wiring loom or the plugs on either side.

 

Yeah, the Bentley matches your sheets. I'm suspicious of the 7.5 V you measured at the plug. The Bentley says that should be battery voltage.

 

Me too. As you said, this measurement should be taken to a ground point on the chassis, not to pin 1.
OP - is this how you measured it?

 

I've checked voltages today on all 3 pins with the key in the "ON" position and received the following:

Pin 1 brn/gry = Signal wire - Pulling 000.7 mV
Pin 2 blk/gry = Ground wire - Pulling 5.01 V
Pin 3 red/blu = Power wire - Pulling 12.05 V

This is obviously not matching anything you've mentioned above so I'm not sure what to make of this.

 

Hmm. Well, pin 2 is the signal wire, and the pin 1 is the ground. The Bentley shows the max voltage on pin 2 as 5 V, so that's not too out of the ordinary. It shows 0 V as the output during the reluctor gap, so the sensor only outputs a voltage when a tooth from the reluctor passes the sensor.

Since this is a Hall effect sensor, it seems to me like you should be able to get a steady 5 volts on the signal line if a tooth is sitting in the sensor field. Someone correct me if my reasoning is wrong. You should be able to bump the key to move the reluctor and get a different reading on the signal line. You could even watch your meter output while you're cranking. It should read less than 5 V, and if the Bentley is right and 2.5 V is the output at idle, then you should read less than 2.5 V while cranking because the rpm should be lower than idle speed. I think the duty cycle at idle would be 50% if the spec is 2.5 V on a regular DMM.

If I had the time, I would go out and stick a meter and scope on my sensor. I've been putting off changing my crank sensor o ring for quite some time, but I've been pretty busy lately.

 

So should Pin 3 (Power) and Pin 1 (Ground) have continuity between them on this sensor? Every time I try to get to the bottom of this, I keep coming back to the likely possibility that the sensor itself is bad. If I'm not getting a closed circuit between power and ground, would that not indicate a failed/faulty sensor?

Of course I also find it difficult to believe that both of the new sensors I received were bad out of the box.

 

I'm not an expert on these, but from looking at some simple block diagrams, no, I wouldn't necessarily expect continuity. That sensor probably has at minimum a linear voltage regulator, some op-amps, etc. in addition to the Hall effect device itself. The fact that you got 5 V on the signal line says that it's at least partially functioning.

Ideally, you would back-probe the signal wire with a scope and look at the waveform while cranking the engine over. Then you could make sure you're getting a nice square wave output.

By the way, you should probably be careful about checking continuity on these. I expect it's fine to do on the power and ground pins, but I don't know how well the sensor would cope with current on the signal line. I'm not really an analog design guy though.

 

Did you remember to put (snap) the connector back onto the crank sensor before buttoning it all up ? Connector look ok ? OEM Part used or aftermarket ?

 

Yes - I've reseated the plug firmly and made sure the red securing clip is snapped in too. This is an OEM crank sensor with the OEM plug on the wiring harness. Everything looks to be in great condition.

I've thought about taking the pins out of the connector/plug to do some inspection but I'm not sure which tool I need to get them to back out. There are so many pin removal tools but I'm not certain of the exact one needed for this type of plug.

 

In my mind this is the only way to properly diagnose the sensor. If the sensor checks out I would look to the DME.
It's entirely possible that when changing out the the sensor o-ring the OP inadvertently touched one of the pins on the harness and fried the DME from ESD. It doesn't take much and it's a precaution that's often overlooked.

 

I can honestly rule this out - DME was removed from the car way before messing with the sensor and the battery had been fully disconnected for a few days before any work started. It's also functioning normally in every other aspect so I feel confident there are no issues with the unit.

 

Just wanted to give a final update on this issue.

It turns out that both of the brand new OEM sensors that I purchased from ECS were bad/faulty. After checking everything I could short of using an oscilloscope to measure the square waves off the Crank Sensor, I went ahead and bought another sensor directly from MINI. Cleared the codes and boom! Car fired up right away.

Thanks to everyone for the help with this issue. Super appreciate all of your input. Happy Motoring!