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Mystery problem:Throttle/pedal position sensor codes Good Auto Electrician?

3K views 1 reply 2 participants last post by  PURPLE_2L_LX 
#1 ·
Update on mystery problem.

First, a reminder of the issue below:

My car is a MK 4 Mondeo 2.0 Ghia 09 plate 108,000 miles approx. Car keeps jerking and cutting out after I've driven a few miles (between 1-10 miles) and throwing an Engine Malfunction warning. Also, sometimes it won't start again for 15 - 20 mins after. The car drives ok with no problems when not presenting with this issue; it also seems to be worse in warm/hot weather.

I took it to a local repair shop a few weeks back and they said the fault was with the throttle position sensor so they replaced that. However, that did not resolve the issue and the problem still remains. Another garage said they could not find any mechanical faults and suggested I use an Auto Electrician.

So, I have a new throttle position sensor, but the problem still remains and I'm still getting codes relating to a throttle/pedal position sensor problem. I have the codes relating to the issue from the garage and from my own OBD II scanner. Codes are as follows:

Code: P0121 - Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance

Code: P0122 - Throttle/Pedal Position Sensor A Circuit Low Input

Code: P0221 - Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance
Code: P0222 - Throttle/Pedal Position Sensor B Circuit Low Input
Code: P2135 - Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation

Also getting a few other codes not related to this issue such as U codes for steering angle sensor module, air conditioning (not sure if this is relevant, but included it just in case)

I have spoken to one Auto Electrician and contacted a few others and am waiting for replies. The one I spoke to said it sounded like a wiring problem but could also be the ECU. Now, I know there is a significant difference in cost between repairing faulty wiring or connections and a replacement/repair for an ECU. Also, I believe it is rare for ECUs to fail? Is there any way of knowing if it is wiring or ECU as the Auto Electrician seemed keen to push the idea that it's an ECU problem (Also said he's really busy right now and seemed a little reluctant if honest). I ask this as I've been told certain garages just default to telling you its a faulty ECU when it isn't.

Can anyone advise as to how much this will cost. 1). For wiring repair. 2). Replacement or repair of ECU? Also, is a second hand ECU feasible?

Any advice/opinions on whether it's a wiring/connection problem or ECU problem really appreciated.

Many thanks
 
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#2 ·
You need someone that is not going to just keep throwing parts and your

money at it until its fixed.

Someone that can hook up to a scope and see the data the throttle is giving

and comparing that to the data the ECU is receiving.

Also battery/charge voltage can affect other sensors down the line.

Just because an LED says the connection is good does not mean its good enough

to carry current.

Fell for that myself Voltage at the socket, voltage coming out of the socket.. Voltage

at the bulb connector yet no light. Bulb is good. Remove bulb and there is 12v, fit the

bulb and still no light. Turned out the wire was broken and only allowing a tiny current

to flow, just enough to light en LED. As soon as the bulb got fitted the connection failed

and no power. Couple of hours of head scratching on that one.
 
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