Throttle pedal position sensor

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Colin2206
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Throttle pedal position sensor

Post by Colin2206 »

The car is a 2008 1.6 VTI.
I've been having multiple problems with the car over the last year, which I've listed elsewhere.
I am now getting getting P2123 which is the Throttle Pedal position sensor. The car runs very rough at idle and responds slow, hesitantly, without any power.
Now I understand that there are two sensors, one at the pedal and one at the throttle. I've taken the pedal & sensor off, because it was the easier to get to but can't find any instructions to test it. So that is what I am after; it has five pins and is marked 9681 4343 80-00.
I started the car without it and it idled at about 1100 rpm, a little rough. I switched off and refitted the pedal and it again started and idled at about 1100 but depressing the pedal made got no response. That suggests the pedal but I've had so many intermittent faults I want to make sure I'm not getting false signals.

Regards,
colin
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GiveMeABreak
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Re: Throttle pedal position sensor

Post by GiveMeABreak »

Here's the descriptor for this fault code as it relates to your specific engine ECU.

The accelerator pedal contains 2 tracks of data and these are compared with each other to ensure they are both reading the same info. If one of the tracks is worn or the connector / wiring is faulty then you can get a mismatch.
Fault Code: P2123
Description of Fault: Butterfly position sensor signal fault: 2 signal: Short circuit to positive. The voltage of the butterfly position sensor (track 2) is higher than 4,7 V for at least 0,14 seconds. The fault is triggered when the Engine management ECU is in main triggering phase.
Conditions for Fault to clear: The following conditions have to be met (For 0,10 second):
  • No fault codes found: P2123 - P2122 - P2121
  • Engine running
  • Programming of the throttle unit is not in progress
  • Motorised throttle housing power stage not cut
Downgrade Modes whilst Fault is active:
  • Application of the down-grade mode "downgrading of driver control"
  • Possible deactivation of the hill start assistance
  • Deactivating the cruise control
Symptoms:
  • Lack of power
Suspect Areas:
  • Motorised throttle unit
  • Electrical harness
  • Connectors
  • Engine ECU

Motorised Throttle Housing

The variable valve lift at the intake system does not require a motorised butterfly housing in order to meter the quantity of air admitted.

The motorised butterfly housing permits:
  • A vacuum of 50 mbar in the air inlet manifold, necessary for the intake of the petrol vapours from the canister and of the recirculated oil vapours
  • A back-up mode in the event of the failure of a component of the valve lift system
An accelerator pedal sensor translates the driver’s request to the engine management ECU.
A dual sensor incorporated in the motorised butterfly housing enables the engine management ECU to determine the exact position of the air butterfly.

If a fault occurs on a component of the variable valve lift system, the engine management ECU manages the air intake by means of the motorised butterfly housing.
207 valve lift A.JPG
(4) Motorised throttle housing.
207 valve lift.JPG
"C" : Position of the butterfly at rest (ignition off) or "limp home" position in the event of a failure.
"D" : Position of the gas butterfly with the ignition on or at idle.
"E" : Position of the butterfly at full load.
(4f) Force of the butterfly motor.
(4g) Force of the spring.
With the ignition off, the "limp home" spring holds the butterfly open(See "C").
When the ignition is switched on, the engine management ECU controls the butterfly to the idle position, countering the force of the "limp home" spring (See "D").
When the engine is idling the throttle butterfly moves to supply the airflow required by the engine (Replaces the idle regulation stepper motor).
From 1500 rpm the engine management ECU controls the throttle in the opposite direction to assist the "limp home" spring (See "E").
The position of the throttle is monitored by the engine management ECU (potentiometer incorporated in the butterfly unit).
The engine management ECU cuts off the supply to the butterfly housing if certain faults are present.
ESSENTIAL : Do not attempt to adjust or dismantle a butterfly unit (safety).

Allocation of channels of connector:
  • Terminal 1: 5 volts supply
  • Terminal 2: 2 signal
  • Terminal 3: Earth
  • Terminal 4: 1 signal
  • Terminal 5: Positive control
  • Terminal 6: Negative control
Colin2206
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Re: Throttle pedal position sensor

Post by Colin2206 »

Thanks Marc; I'll need to read this a bit to make sure I understand it.

To be clear the butterfly flap should be partially open at rest (no power) and crack open on ignition before starting? Thats an easy check.
To check operation of the pedal: I should look to get 5v at Terminal 1 and if so , then get the reading at Terminal 2 which should be the same value as at Terminal 4 and the value should change in unison with the pedal position, and the value at all times should be less than 4.7v. I'm not sure what Terminals 5 & 6 do. Do they need to be checked and if so for what? (I have a basic digital multimeter but could possibly borrow a more sophisticated device if it is needed.)

The car is on the drive and it is begining to rain, so I'll try this tomorrow. The pedal connector is tight to get to but I'll try there first because the throttle body & connector is really awkward to get to.
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GiveMeABreak
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Re: Throttle pedal position sensor

Post by GiveMeABreak »

Here's the wiring and Pin outs for the accelerator (1261):
207 TPS Diag.JPG
1377: Accelerator pedal 1 position info
1379: accelerator pedal position earth
1378: Accelerator pedal 2 position info
1380: + 5 volt accelerator pedal position indicator power supply
731B: accelerator pedal point of resistance / signal

These are the ones for the Motorised Butterfly Throttle (1262):
207 Butterfly Diag.JPG
1218: throttle potentiometer position signal 1
1220: throttle potentiometer supply 5V
1219: throttle potentiometer position signal 2
1367: motorised butterfly potentiometer earth
1372: Throttle motor command by -
1371: Throttle motor command by +
Colin2206
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Re: Throttle pedal position sensor

Post by Colin2206 »

Thanks again for this. I studied it last night, printed it off and made myself an order of tests to do.

So this morning I went out, identified the ECU, the correct plug, unplugged it and found the bottom wet with blue water. Can't figure out the blue, the only thing blue is the window washers. I did have a blown expansion tank pipe a couple of months ago but the anti-freeze is pink. Anyway, I took the ECU off the car, onto a bench dried it with cotton buds, then alcohol, then the wife's hair drier, lightly scrapped the blade connectors with a fine screw driver, repeated, then did the same with the plugs. None of the male connectors were heavily marked/corroded, although harder to say about the plug end. Re installed and got the same P2122 & P2123 errors but all other errors disappeared (positive result). The car is in limp home mode, the butterfly valve is cracked open and returns to closed when ignition is off.
So, I'll be doing the checks re pedal later today/tomorrow. Question is how do you access the terminals on the plugs? I'm guessing the latch mechanism comes off; the cable anchor is a cable tie and there seems to be press in tangs to release the terminal block? Is there anything else to releasing the terminal block? Don't want to find I do something irreversible at this stage.
Hell Razor5543
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Re: Throttle pedal position sensor

Post by Hell Razor5543 »

I would use something like a proper contact cleaner, sprayed into the plug and then plug and unplug it several times, so the action will help scrape off any tarnish/corrosion that you cannot get to.
wheeler
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Re: Throttle pedal position sensor

Post by wheeler »

Colin2206 wrote:
30 Mar 2022, 12:08
Question is how do you access the terminals on the plugs? I'm guessing the latch mechanism comes off; the cable anchor is a cable tie and there seems to be press in tangs to release the terminal block? Is there anything else to releasing the terminal block? Don't want to find I do something irreversible at this stage.
Once the latch & top cover are off you also need to slide this bit out. On the face of the connector there is a little hole above the terminal, you then need to push something very small like a sewing needle into the hole to push a barb on the terminal in to allow you to release it.
I know you said you anti freeze is pink but just double check by unplugging the coolant temp sensor & check for signs of coolant in the plug, its not unknow for the temp sensor to crack & allow coolant to travel up the wiring harness.
Just a heads up, if there are signs of water in the plug there's a good chance its been getting in there for a while before you noticed any issues & more often than not has been working its way inside the ECU for a while & corroding the circuit board. Seen it many times in similar scenarios & have found that cleaning the plug & ECU terminals is short lived & ends up needing the ECU replaced or repaired.
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Colin2206
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Re: Throttle pedal position sensor

Post by Colin2206 »

Hell Razor5543; Yes, I'll be doing this and when I finish with this job I will use electronic sealer (because there is a can in the garage).

It seems that keeping the ECU in doors and the plugs lying in the sunshine has got the last bit of dampness out, the car is running (not well but no worse than for the last few months, possible head gasket problems).

wheeler ; I was looking at this, I took the latch & cover off earlier. I seen the green clip but was relucant to move it as I wasn't sure how easy it would go back together. However, as the car is running and no faults showing, I'll leave it for now. I understand what you say about the ECU itself and I have other problems to resolve first.

Thanks again for your help.
gwest
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Re: Throttle pedal position sensor

Post by gwest »

Colin, the blue colour is almost certainly because copper salts are being formed due to water ingress like wheeler describes. If the corrosion only happens at the ECU connection then I can see how cleaning it up may help but if it corrodes the affected wires in the loom then it could be a real pain.
Colin2206
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Re: Throttle pedal position sensor

Post by Colin2206 »

Thanks for this.
Blue copper salts are usually crusty when dry and smudge when wet, in my experience. This was blue coloured water, I still don't know its origin. However, I seem to have caught it just in time, the pins are all clean and no visible corrosion. Drying it out in the Sun also seems to have done the trick.
Engine still sounds lumpy to me, on start up and idle. Revs ok and the MIL light is off and no codes stored and have been using it with easy miles for the last few weeks with no problems.