Acc. Pedal Position

Ask for and share advice on using the PicoScope kit to fix vehicles here.

Acc. Pedal Position

Postby Dundeeguy » Tue Jun 04, 2013 9:18 pm

Hi guys,

Had an Astra diesel go into limp mode. Code read and had a couple of codes for accelerator position sensor tracks 1 and 2.

So, thought this can be tested with the scope and off I went. On zooming in on the attached waveform I could see the signal drop off slightly every so often on track 2 (blue trace) Bingo, proud as punch got the boss to order a new part. Only problem being, the new part does the same!! :oops: :evil:

Car goes fine and no codes getting logged, just looking for thoughts on the waveform.

Thanks,

Kevin
Attachments
Astra APP.psdata
(617.75 KiB) Downloaded 304 times
Dundeeguy
User
User
 
Posts: 40
Joined: Thu Apr 11, 2013 1:13 pm
Location: Emm, kinda obvious!

Re: Acc. Pedal Position

Postby modo » Tue Jun 04, 2013 9:52 pm

See if it happens on the power and ground circuits of the unit to isolate the drop out. It happens at a constant rate of approx 170mv looks like something is switching on and off may have to go to the throttle body and see if you get the same result there.
modo
User
User
 
Posts: 21
Joined: Thu Jun 21, 2012 10:02 pm

Re: Acc. Pedal Position

Postby Valhalla » Tue Jun 04, 2013 11:05 pm

Looks like something switching at a period of 320ms constantly, probably on the track 2 voltage positive line. Seems to be a proportional drop-out depending on the sensor output signal, as you can just see the same drop-out throughout the APP = 0% part of the trace. Would that conclusively make it a positive line problem? Certainly, whatever it is that is causing the APP2 sensor signal to fail, it has got a very constant period of 320ms. Might be worth checking a wiring diagram to see what else is on that sensor supply line....

If I were your boss, I wouldn't blame you. Thought for the day.
Valhalla
Advanced User
Advanced User
 
Posts: 66
Joined: Sat May 18, 2013 10:22 pm

Re: Acc. Pedal Position

Postby Darren Cotton » Thu Jun 06, 2013 8:17 am

How did you get on with this?

is it an astra H?

Darren
Darren Cotton
Advanced User
Advanced User
 
Posts: 52
Joined: Thu Jun 16, 2011 9:53 pm

Re: Acc. Pedal Position

Postby Robski » Thu Jun 06, 2013 9:20 am

Darren Cotton wrote:How did you get on with this?

is it an astra H?

Darren

Are you thinking what i'm thinking :?:
User avatar
Robski
Advanced User
Advanced User
 
Posts: 602
Joined: Tue Sep 14, 2010 6:36 pm
Location: Yorkshire

Re: Acc. Pedal Position

Postby Dundeeguy » Thu Jun 06, 2013 9:20 am

Ok, car came back today!!

Checked earths and 5volt feeds at multiplug. All spot on. Track 2 drops voltage same as before. Have tested both 5volts and earths when it happens, and both remain stable :? Everything has been checked at pedal.

Went and carried out tests as per vauxhall tech info, and it tells me to replace the pedal :x I can't see us being unlucky getting a faulty part that does the same.

Darren, it is an Astra H on a 54 plate fitted with the 17DTL engine.

Awaiting the customer calling to confirm exactly when and how fault happens.

Cheers
Dundeeguy
User
User
 
Posts: 40
Joined: Thu Apr 11, 2013 1:13 pm
Location: Emm, kinda obvious!

Re: Acc. Pedal Position

Postby Darren Cotton » Thu Jun 06, 2013 10:14 am

Have you actually looked at a wiring diagram for the pedal?


Darren
Darren Cotton
Advanced User
Advanced User
 
Posts: 52
Joined: Thu Jun 16, 2011 9:53 pm

Re: Acc. Pedal Position

Postby Dundeeguy » Thu Jun 06, 2013 12:53 pm

Just trying to browse the diagram while having a bite to eat and speak to customers!

I see it seems to pop through the instrument cluster, then through underbonnet fuse box then onto the ECU.

Would these other components cause the track 2 voltage to drop out? The 5volts remains constant for the tracks, and I'm measuring at the pedal. I could understand it happening if I were testing at the ECU??

I'm obviously missing something here. Now starting to think the drop out isn't causing the fault and is normal!

Cheers
Dundeeguy
User
User
 
Posts: 40
Joined: Thu Apr 11, 2013 1:13 pm
Location: Emm, kinda obvious!

Re: Acc. Pedal Position

Postby KimAndersen » Fri Jun 07, 2013 9:34 am

Hi.

I was wondering if the new APP sensor should be adapted to the PCM ?

I know that some cars with APP sensors use adaptation and others don´t.

With the serial tester connected what values are you getting from the APP sensor in terms of percentages ?

Regards
Kim
KimAndersen
Guru
Guru
 
Posts: 159
Joined: Fri Nov 30, 2012 2:53 pm
Location: Denmark

Re: Acc. Pedal Position

Postby Valhalla » Fri Jun 07, 2013 11:33 pm

Dundeeguy wrote:I see it seems to pop through the instrument cluster, then through underbonnet fuse box then onto the ECU.

Would these other components cause the track 2 voltage to drop out? The 5volts remains constant for the tracks, and I'm measuring at the pedal. I could understand it happening if I were testing at the ECU??

I think that you are going to have to temporarily pull the pin for APP2 signal input to the EDC15C7 controller, and then see if the signal you are measuring at the pedal for track 2 is still being pulled down. No question that whatever is causing the problem is very consistent; period is exactly 320ms, pull down is by 6.6% (+/- 0.2%) of the signal voltage. If you had a spec for the pedal track resistance, you could probably work-out the load impedance that is being applied.

I have been wracking my brains for the things that operate on a 320ms cycle. Assuming that this isn't the ECU (i.e. problem does not go away by pulling the APP2 signal pin at the ECU), then it is likely that the instrument pack is a gateway to something else that wants the throttle pedal signal (transmission? abs? ) but hasn't been set-up with the signal directly from the ECU over a CANbus.

I really hope you fix this one, so I can get some sleep. :roll:
Valhalla
Advanced User
Advanced User
 
Posts: 66
Joined: Sat May 18, 2013 10:22 pm

Next

Return to Diagnostic discussion

Who is online

Users browsing this forum: No registered users and 0 guests