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Astra H 1.7 CDTI Cam sensor P0340 **FIXED**

Posted By TG 5/3/2011 3:50:44 PM
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TG
 Posted 5/3/2011 3:50:44 PM
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2006 Astra Z17 DTH engine.

Intermittent P0340 cam sensor open circuit, always starts and runs OK.

It appears to have a hall effect cam sensor, terminal 3 is batt voltage supply which is good, IIRC term 1 is earth, again that's good. Terminal 2 is a 5v feed from the ECU which according to autodata is switched to 0v when the metal plate passes the sensor.

The scope shows the sensor switching, the waveform is regular and clean but it's switching from 5v to only about 2.5v.

Should I assume the sensor switching circuit has a high resistance and condemn it? I don't see what else it could be.

Thanks.
5/5/2011 4:57:51 PM by TorGarage
opelboy
 Posted 5/3/2011 5:03:56 PM
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Is there any fault when driving the car ? Does it go in to limp mode when the engine light illuminates ?
RichTT
 Posted 5/3/2011 5:25:39 PM
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Hi,

Haven't checked AD but wouldn't expect 0v as this would be seen as a fault by ECU however, 2.5v doesn't sound right either.

Do you have the other 2 digits of the fault code? P0340-xx?
TG
 Posted 5/3/2011 5:28:10 PM
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I've not been driving the car myself when the light has come on but the owner has reported a reduction in power when the light is one. I have noticed it takes a little longer to start when the fault is there and live data on solus shows either 0 or a default value of 450 rpm. The light is the big spanner on the car one..

TG
 Posted 5/3/2011 5:31:48 PM
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AD deffo says 0 volts which is why I assumed that the signal wire was switched to ground.

I'm using solus pro, all I'm getting is P0340 cam sensor open circuit...
RichTT
 Posted 5/3/2011 6:05:30 PM
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OK.

I personally would expect close to 0v but not actually 0v. 2.5v is wrong for sure.

Did your description on solus actually say open circuit?

Reading 2.5v I would expect it not to start without alot of cranking?

Can you post your scope pattern vehicle running?

TG
 Posted 5/4/2011 5:09:41 AM
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It does say open circuit, yes.

It actually starts pretty well even with the sensor unplugged which I was surprised about!

I have scoped it again this morning, now it's all cold again the fault code clears and the voltage is switching to nearer 1v so I'm pretty sure the engine heat is making the resistance in the circuit increase.

Going to fit a new sensor now...
TG
 Posted 5/5/2011 4:57:11 PM
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The new sensor saw it switching to 0v (or as close as I could tell on my old CRT scope) and all is well with the astra again! BigGrin

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