P0340 code after Head gasket replacement

[Mechanic-al]

Please skip to the next paragraph to skip my intro.
Sitting at a desk is not how I want to spend the rest of my life, so I've decided to become a mechanic.
They say "if your job is your hobby, you'll never work a day in your life."
I've always enjoyed resurrecting things that others deem knackered, so here I go !
Pushing my limits, trying to learn as much as possible, so I'm not 'green' when start my mechanics career.

'53 Suzuki Jimny.
Replaced the head gasket.
Can't get rid of P0340 camshaft sensor code after head gasket replacement.
Photos to prove timing chain was fitted correctly when it went back together.
Can clear the code but it reappears at every start up.
New alternator a year ago, fine before head came off.
Replaced OE Denso camshaft sensor with BluePrint equivalent; no difference.
12V & 5V supplies to sensor are present.
What should I be doing / checking ?

All comments gratefully received.

 

[brianmoooore]

Is the cam sprocket fixed to the camshaft in one immovable position in this engine?

 

[Mechanic-al]

Hi, thanks for replying.
Yes, the camshaft sprocket is a single item, see image attached.
As they came out, they went straight in a box and stayed there until reassembly.

I did some more digging last night...
As is, the car starts as normal (about 1 second of cranking before firing), and the appearance of the error code is instantaneous.
With the sensor unplugged, the engine fires but takes about 5 seconds of cranking, showing that sensor is at least partially working.
It also occurs to me that if the 0V of the camshaft connector is an fact Earth, I could run a new wire directly to the chassis to check it's not a bad earth.
I'll need to check the wiring diagram.

 

[newfutile]

Check your earth and power to the sensor as a basic precaution, they are ok you will need to either scope the obd from the sensor , or swap for a known good sensor

 

[Mechanic-al]

Check your earth and power to the sensor as a basic precaution, they are ok you will need to either scope the obd from the sensor , or swap for a known good sensor

The 5V & 12V are present but can't judge quality or consistency as I don't have a scope.
Finding a known good sensor will also be tricky, but I'll ask around.
Sounds like I'm headed for an auto-electrician shop near me.

 

[DPG]

As far as I know there will be no intelligence in the camshaft sensor, so it may well be possible to test it while manually turning the engine slowly. The reading on a meter will hopefully show a variation at just one point in a full rotation of the camshaft (assuming there is only one indent or whatever on it).

When you say you have the 5V and 12V references, only one of these will be a reference - the other will most likely be the output to the ECU.

 

[newfutile]

I’m not sure why you would have 12 and 5 volts as the reference .i assume its a 3 wire type.
try this place to learn more 3 Wire Crank Position Sensor Wiring Diagram - https://toolsweek.com/3-wire-crank-position-sensor-wiring-diagram/

if the sensor is working and the power/reference and ground are correct and stable then it may be the sensor out wire to the ECU is broken

 

[brianmoooore]

Are those camshaft sprockets integral with the camshaft itself? There's no sign of a fixing in the exploded diagram.

 

[Mechanic-al]

As far as I know there will be no intelligence in the camshaft sensor, so it may well be possible to test it while manually turning the engine slowly. The reading on a meter will hopefully show a variation at just one point in a full rotation of the camshaft (assuming there is only one indent or whatever on it).

When you say you have the 5V and 12V references, only one of these will be a reference - the other will most likely be the output to the ECU.

Hi,
My understanding is that on a 3 wire sensor, there is a reference voltage, signal voltage and 0V.
Metering has shown that there is:
1. a constant 12V, I have assumed this is the Reference voltage.
2. 0V, I now understand this to be 'earth'.
3. 5V that fluctuates if I interrupt the flux with a metal ratchet. I have assumed this is the Signal voltage to the ECU.

 

[DPG]

Hi,
My understanding is that on a 3 wire sensor, there is a reference voltage, signal voltage and 0V.
Metering has shown that there is:
1. a constant 12V, I have assumed this is the Reference voltage.
2. 0V, I now understand this to be 'earth'.
3. 5V that fluctuates if I interrupt the flux with a metal ratchet. I have assumed this is the Signal voltage to the ECU.

Yes I would agree with that.

 

[Mechanic-al]

I’m not sure why you would have 12 and 5 volts as the reference .i assume its a 3 wire type.
try this place to learn more 3 Wire Crank Position Sensor Wiring Diagram - https://toolsweek.com/3-wire-crank-position-sensor-wiring-diagram/

if the sensor is working and the power/reference and ground are correct and stable then it may be the sensor out wire to the ECU is broken

Hi,
Yes, it's a 3 wire sensor. The link says I can meter the resistances of the sensor, so I need to check my manual for the correct values.
It is a new one though so I'm not expecting that to be the issue.
It also says the 0V is actually Ground, so I can run a new wire to check that, and rule it out.
"Expect the unexpected, Grasshopper!"

 

[DPG]

Hi,
Yes, it's a 3 wire sensor. The link says I can meter the resistances of the sensor, so I need to check my manual for the correct values.
It is a new one though so I'm not expecting that to be the issue.
It also says the 0V is actually Ground, so I can run a new wire to check that, and rule it out.
"Expect the unexpected, Grasshopper!"

Have you tried using a voltmeter yet while rotating the engine by hand? Will need ignition to be on. I'm pretty sure you should see the voltage change when the sense point is passed. Brian will hopefully advise if I am wrong with this!

 

[Mechanic-al]

Are those camshaft sprockets integral with the camshaft itself? There's no sign of a fixing in the exploded diagram.

Hi,
Yes, I guessed they are assembled with heat, with an interference fit. I couldn't identify the joint so treated them as single components.

 

[Mechanic-al]

Have you tried using a voltmeter yet while rotating the engine by hand? Will need ignition to be on. I'm pretty sure you should see the voltage change when the sense point is passed. Brian will hopefully advise if I am wrong with this!

I have not tried that but I will do so asap.

 

[brianmoooore]

Hi,
Yes, I guessed they are assembled with heat, with an interference fit. I couldn't identify the joint so treated them as single components.

In that case, if it's not adjustable, we can discount that as the cause of the problem.
Are there tensioners on both runs of the chain from the crank sprocket to the cams? If so, do they both appear to be doing their job? One deflecting the chain more than it should, at the expense of the other, will affect the cam timing.

 

[Mechanic-al]

In that case, if it's not adjustable, we can discount that as the cause of the problem.
Are there tensioners on both runs of the chain from the crank sprocket to the cams? If so, do they both appear to be doing their job? One deflecting the chain more than it should, at the expense of the other, will affect the cam timing.

Excellent question, I love the way you're thinking outside the box.
There is what I would call 'aligner' and one tensioner.
When looking at the front of the engine, it rotates CW (Clockwise).
The exhaust camshaft (with sensor) is on the left and the chain runs in a perfectly straight line down to the crankshaft.
This tensions the chain over both crankshafts and the crankshaft, ensuring no tensioner is required to 'time' them.
The tensioner is on the slack (return) side between the crankshaft and inlet camshaft.

 

[brianmoooore]

Difficult to see how anything could go wrong with that tensioner arrangement that would affect the phasing of crank and cam.
Clutching at straws now. The crank sprocket appears to be separate from the crank. How is it located on the crank?
Presumably there are timing marks on each cam pulley. What/where is the crank timing mark?

 

[Mechanic-al]

Difficult to see how anything could go wrong with that tensioner arrangement that would affect the phasing of crank and cam.
Clutching at straws now. The crank sprocket appears to be separate from the crank. How is it located on the crank?
Presumably there are timing marks on each cam pulley. What/where is the crank timing mark?

Hi,
The crank sprocket appeared to be an integral part of the crankshaft. I tugged on it a bit and it didn't budge so I left it alone.
Re-assembly instruction include reference to coloured links. A silver one aligns with a dot on the crank sprocket and blue ones align with markers on the cams. Also other marks on the cams and head to ensure alignment is correct.
After re-assembly the engine was given somewhere between 10-20 revs until the chain links realigned with the marks on the crank and cams. All seemed A-OK at the time when I replaced the timing cover.

 

[brianmoooore]

Only thing I can think of now is to check that the crank timing mark really does correspond to TDC. This is normally possible to check with a dial gauge, through #1 spark plug hole, onto the top of the piston. Check that the crank mark corresponds to the piston at its highest point.

 

[Mechanic-al]

Only thing I can think of now is to check that the crank timing mark really does correspond to TDC. This is normally possible to check with a dial gauge, through #1 spark plug hole, onto the top of the piston. Check that the crank mark corresponds to the piston at its highest point.

Good call.
I don't have a dial indicator, but I once did this check on a 2 cylinder bike engine with a screw-driver down the plug hole. It worked a treat.
I was about to ask which is the #1 cylinder but since it's going to be at one or other end, and both those crank journals are at the same angle, it doesn't actually matter.