Hi

 

First post here, hoping to get some advice on a strange and annoying issue I've got on my wife's polo.

 

Background of the issue first, car was fine but then developed rough idling and sometimes struggled to start. I plugged a code reader into the OBDII port and got a P0322 code (current & pending), Ignition/Distributor Engine Speed Input Circuit No Signal. After looking into it, it seemed highly likely it was the Crankshaft Sensor that was the issue so I replaced this with a new Bosch sensor from ECP, but the problems still exist. The car does start and run however the rev counter doesn't work and the code comes straight back if cleared whilst running. The engine code is BBY and I'm confident I got the right sensor.

 

With the ignition on I have tested voltages between pins 1 & 3, which results in 3.0v, I have also tested the voltage on the signalling pin but that reads 2.9v regardless of whether the engine is being cranked or not. From everything I've read, this isn't the desired behaviour.

 

I can't find any further information, clues etc online and am rather at my wits end now. If anyone can point me in the right direction, it would be hugely appreciated.

 

Many thanks

Check continuity from pin 1  of crank sensor connector to pin 87 at engine ECU, and from pin 2 to pin 82.

What was/is the Bosch part number of what you've fitted?

Edited 26 March, 20215 yr by Pete1

First Welcome to the Forum.

 

The first thing DO NOT buy sensors from the likes of ECP/GSF the quality of the apparent genuine sensors is terrible, did you change the correct sensor ?  as your engine has two, the crank sensor G28 is the awkward one at the rear of the engine down by the joint between the engine & gearbox, the cam sensor G40 is the easy one to replace on both sensors pins 1 to 3 should be around 5v and pin 2 to 3 pulsing 5v as the engine is running. 

Thank you for the pointers!! I have checked continuity from pin 1 to pin 87 and from pin 2 to pin 82 and both return just fine. Whilst I was doing that, I checked to make sure that there's no crossed wires by checking the other pins on the sensor plug against 87 and 82 on the ecu plug, those tests returned negative.

 

The Bosch part number is 0261 210 257.

 

That's an interesting question about did I change it for the correct part as I can't be 100%. Reason for this is someone else looked at the car before I did and they changed the old crankshaft sensor, so effectively the one I've just fitted is the second brand new one, which was the same as the other new one I removed, I don't know what the original looked like though. I did check as extensively as I could before buying another sensor.

 

I'm going to put it back together now and check the voltages again.

Plugged the ECU back in and tested the voltages again, still something not quite right.

 

Pin 1 & 3: 4.63v

Pin 2 & 3: 4.44v

 

Tested the signalling pin (no. 2) again whilst cranking the engine but no voltage changes at all.

What are you measuring with? The output is likely to be a pulse train I would think, with a missing or wider pulse once a revolution, or some such thing, so not something a multimeter could 'see'.

 

That Bosch part number does seem to be correct, unless your VIN has a 3 as the 10th digit and the tail end of the number is less than or equal to 145000.

Just using a normal multimeter as that's all I have. I've seen it mentioned a couple of times across different post, re testing the voltages for 4v+ between the different pins so thought that is what I was supposed to be doing.

 

The VIN is WVWZZZ9NZ4Y183909 so that would indicate it's the correct part.

 

Any ideas what I can be looking for next please? 

If you're turning the engine over by hand a normal multi-meter might show the pulses ( old fashioned moving coil meters with a pointer show better than a digital display) but if you're trying with the engine running you'll need an oscilloscope to see the pulses and the missing pulse for TDC