TPS error 12, replace or adjust?

[Chief Brody]

Hi all. Having a bit of an issue and thought I’d keep it documented here as it might be helpful to others in the future. A couple of times whilst I’ve been driving, the hold light has started flashing and the car starts acting unpredictably. Revving highly, dropping speed etc. It’s hard to be more specific but it’s only happened twice and didn’t last long at all the first time. The second time the hold light stayed on for a lot longer but the effect on the transmission wasn’t as pronounced after a few minutes. After searching here, I opened the diagnostic box and did the appropriate link as detailed in other threads. I got an error code reading of 12 and 16 which was based on 1 long flash, 2 short flashes, 4 second gap, 1 long flash, 6 short flashes. I disconnected the negative on the battery, put the key in the ignition and pressed the brake pedal until all residual power was used up. This reset the fault codes stored in the system. I then went for a drive, hit an A road, pushed it to 60 and within a few minutes the revvs started and the hold light started flashing. Pulled in to layby and read the flashes. This time it was only a 12 code. This kept flashing until I got home.

The threads here lead me to believe the problem lies with the Throttle Position Sensor. Now, at this point, I’m trying to work out if it merely needs adjusting or replaced. I have a multimeter and will get access to the ECU later and measure the voltage from the TPS (pin 21) . I think I need to read 1.3V at idle and 4.2V when I’m maintaining a steady speed. If the voltage is bouncing about does this point to a faulty sensor or can adjusting it cure it? I really need to know what can I do to prove 100% that the sensor is faulty before I cough up £150 on a new part. Any help offered will be greatly appreciated.

[g8dhe]

You can try measuring the resistance of the potentiometer as you adjust it manually when disconnected, if it shows any intermitincy it might be better to replace it rather than using a cleaner as I think on the diesel its a "sealed" unit as such.

[Chief Brody]

Thanks g8dhe. I'll have a look into that. Kind of learning as I go here but eager to get this sorted. For my own information, am I right in thinking that to adjust the TPS, I remove the 2 screws holding it in place and adjust it from the other side as in here:



Or do I just loosen the screws and adjust it from the front?

[g8dhe]

I've not done it on a diesel myself, but normally from what others have written its loosen the screws and adjust in position, your rotating the body a little at a time around the spindle that is fixed on the shaft itself. Others have noted that it doesn't need a lot of adjustment, so mark it clearly and tweak a couple of degrees at a time at most .....

[Chief Brody]

Thanks again. That's how I have read it too when I looked at past threads but I just wasn't sure. I suppose it will make more sense when I tackle it later. I think there is a good chance that I may need a new sensor. Not sure why it would suddenly need adjusting. Also confused why it is intermittent. There must be something specific that I'm doing to set it off. I suppose the idea is to adjust it till I get it to line up with the recommended voltages. Will report back to this thread later. Thanks for the help.

[g8dhe]

I believe you will find that its a wirewound potentiometer, so the slider that rotates on the spindle makes contact with the wire and taps off a voltage between the two end contacts, normally they are reliable until either the wire wears out and snaps or dirt gets inside and lifts the wiper off the wire, construction will be similar to below;

[Chief Brody]

Thanks again for taking the time. Got into ECU. Found pin as shown in following photo:

https://i.imgur.com/up7zdGc.jpg

Inserted wire into other side and plugged back in. There was already a wire in that pin so was hard to put my wire in alongside it. Couldn't be sure I was even making contact. Am I doing something silly? Measured positive on multimeter to the wire and negative to the chassis. No reading at all whether engine on our off. Checked multimeter against battery and all working fine. Stumped.

https://imgur.com/gallery/vkBF2eO

[g8dhe]

If your a diesel the connector pin is 2I not 2L which is coolant temperature!

See here

[Chief Brody]

Thanks again Geoff. You're a great help. I should have double checked that pin was for diesel. Regardless, I'm struggling to get my wire in that terminal alongside the other wire. Not sure where to go from here. Thanks.

[Chief Brody]

Just so I know for sure I'm not making a hash of things, can anyone confirm that the following is the correct process to measure the voltage of the TPS?

Locate middle loom as seen here.


Locate pin 2I which should be the TPS (diesel engine)
Insert a wire to this pin (alongside the wire that is already there)
Push connector back into place
Turn ignition to on
Touch positive from meter to my wire in connector
Touch negative to chassis

Is this right? Because of existing wire, I can't even be sure that my wire is making contact. I'm getting nothing. I'm sure I'm doing something stupid. Anyone have any ideas?

[g8dhe]

What you describe sounds right, but what settings have you selected on the meter and are the probes connected to the correct sockets?

[Chief Brody]

Hi Geoff. I'm reasonably familiar with meters and have a 9V battery that I check to ensure all is working. Black into COM and red into V and meter set to 20V. Not sure what I'm doing wrong.

[teenmal]

Would it not be easier to do the tests at the TPS unit itself??.

If you are stuck , there are plenty of Utube videos to explain the process .


Good luck take care.

[Chief Brody]

Thanks Teenmal. As far as I was aware, after reading threads here, the only way to measure the voltage of the TPS was to do it at the ECU.

[g8dhe]

Are you not able to slide the probe into the rear of the connector, rather than trying to push a wire in ?