Limited revs and power down

**Ste** · 13th November 2009, 18:00

Car is limited to 4000 rpm in any gear or in neutral and is less responsive, lumpy and down on power. Also car with spanner through it is on. Fuel economy is also down.

Done the pedal retreival (and diagnostic kit via OBD port to confirm) and getting P0340 fault code - Camshaft position sensor circuit malfunction.

As I'm not into the haphazard replacement of parts I decided to get some test kit out today at work, and did a demonstration to a collegue at the same time (legitimising all the time too ;-) )

Anyway, the output from the sensor seemed plausible and was a square wave form oscillating between about zero and 5 volts, dependant on rpm. As the cam has a semicircular signal ring, the output was approx 50% at 5V and 50% at zero Volts (as expected)

The signal had a small amount of noise, more evident during the cranking of the engine than at stable idle. Unfortunately, I don't have the chart now, as it's at work. Clearly the sensor itself is working.

I guess there are 3 questions,

1 - does anyone know of any other signal logging that I could compare the cleanness of my signal to

2 - anyone have a pin out of the main engine controller, so I can check for eventual electrical continuity

3 - anyone had this problem before or know what specific areas to look at?

1.8 Petrol on 04 plate, 126K miles on clock and first engine problem......
Cheers.

**gav_embo** · 13th November 2009, 18:27

my mate has the same problem on his 1.8 corsa its in garage getting fixed should have it bk on monday will let you know what his problem was

**Ste** · 16th November 2009, 10:33

Here is the chart previously mentioned.

At the weekend I removed and cleaned the sensor and camshaft signal ring. I also checked for electrical continuity between sensor plug and engine controller for all 3 wires from the sensor

Everything appeared to be in order.

Fuel economy is down by approx 15% - which is significant.

Anyway, I think my next action will be to replace the sensor itself - even though it appears to be giving the correct signal.

The trouble started the other week, when we had a bit of cold weather. Morning starts were difficult due to a poor battery. Instead of the normal cranking speed, the engine would crank relatively slowly, and I originally attributed camshaft sensor error to low battery voltage. One new battery later (with much improved cranking ability, and cold start capability) hasn't cured the sensor issue.

I wonder if low battery voltage can actually damage the sensor......? Doubtful

**Ste** · 19th November 2009, 09:55

No-one?

**Grimo72** · 19th November 2009, 10:31

**John C S** · 20th November 2009, 07:47

Unusual fault Ste.

I do know that on my father in laws PT Cruiser, a poor battery caused very poor idle quality and rough running.

Also, a faulty power steering pressure switch in the steering rack is causing a P1684 fault code to report (Battery disconnected in the last 50 starts).

I hope that the cam sensor cures it for you Ste.

That said, father in law also had cam sensor fault, it wasn't the sensor, but chafed wiring to the sensor causing intermittent problems.

**Dose** · 20th November 2009, 09:11

on your symptoms i would say airflow meter problem mate...no one near yopu with a 1.8 to try it..with most airflow meter problems the rev range is limited to 4000rpm.