Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back | Technical matters | Back Room Forum

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Sat 23 Mar 2013 15:36

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - mw01908

Hello all. I took my car to a garage for a diag check - the above code (121 I think) came up. They cleared off the code and the light went off. But as soon as I put the car in reverse WITHOUT touching the throttle, the Engine Management light came back on.

The car drives most of the time ok, but when I start off in 1st gear, the revs sometimes suddenly drop down , making the car lose power and go slow which at times can be dangerous when joining a roundabout etc or in traffic as someone may run into the back or side of me!

The garage suggest a new throttle postion sensor but how can this be the fault if the fault somes back as soon as engaging a gear without touching the pedal, could it be something else??. Does the ECU do some kind of auto throttle when idling in gear to avoid stalling the car? Could it be injection related? The car runs otherwise fine
I would appreciate anyones thoughts on this.

Is the TPS easy to get at to remove and clean out?>

Thanks in advance for any help

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Sat 23 Mar 2013 16:06

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - Collos25

I doubt if you can clean it its a sealed unit plug and play they cost about 8ukps all it does is tell the ECU what position the throttle is.I would replace the TPS but also clean out the EGR as this gives problems so does the turbo if its leaking or the bearings are breaking up .Check to see if you have a electronic turbo actuator as these are notorious for going wrong

.www.ebay.co.uk/itm/Peugeot-806-ACP-Throttle-Positi...e

Edited by Collos25 on 23/03/2013 at 16:21

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Sat 23 Mar 2013 22:04

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - mw01908

Hi thanks for the response. I'll look into the EGR. How do I check if I have an electronic turbo actuator?

I went to that ebay link but when I put in my exact make and model 2.0 HDi it says that part is not suitable for the car. The cheapest TPS I can see on ebay is £60 :-(

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Tue 26 Mar 2013 21:48

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - mw01908

Update: I've ordered an ELM 327 to look at the live data to get more clues. I haven't been looking under the bonnect much as its is siberian cold out there! I did however spray some contact cleaner on the TPS plug and around the housing. It made no difference, in fact now the car is in limp mode under engine load and revs by itself in neutral to about 1500 rpm. If I floor it in neutral often the limp mode is cleared and the excessive revs come eventually back down to normal. I have an oscilloscope and DVM and I planned to use that to test the TPS but have no idea which wire to probe on this 4 wire system, can anyone tell me the expected voltages on these 4 wires please?

The other problem is that the bolts on the TPS bracket/housing are very rusty as it no head left, I don't know how I am going to get it off if I do have to change it! I was also planning to briefly disconnect the MAF to try and eliminate that. Sorry if I seem a bit of a newbie thats because I am - especially to modern ECU driven stuff! Any further suggestions would be great!

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Wed 27 Mar 2013 20:11

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - mw01908

Ok, I did some voltage tests tonight as the car has started losing power at junctions and kangerooed on the way home.

All measured with respect to the battery GND

Red 5v (wire 1391) permanent no matter of the pot position

White (wire 1377) 0.48v No throttle, 3.77v full throttle

Yellow (wire 1378) 0.25v No throttle, 1.90v full throttle

Green (wire 1392) 0v no matter of the pot position, probably this is the circuit GND

I moved the TPS wheel very slowly from rest to full on and back again, and watched the voltage move each time, there were no jumps or any indication of a bad potentiometer.

Now with this info - Surely someone can tell me if this is normal>?? I would summise that the TPS is ok and it must be something else??? But what ? (if I am correct?)

Edited by mw01908 on 27/03/2013 at 20:12

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Wed 27 Mar 2013 20:59

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - injection doc

Could be the engine bay harness, knowing French cars you can do all the testing under the sun but sometimes you end up just taking a loom out, laying it out on a floor and stripping it all back to check for breaks or rubbed through to another wire !
1st check the rear lights , to make sure they are working 100% look out for one slightly dimmer, check with indicators on and barke lights. If you have a poor connection or corroded light cluster the brake light circuit may be feeding back triggering off the throttle cut off. Difficult to explain but have had rear light clusters in French cars confuse auto boxes and engine management systems something chronic,! Remember as bizarre as it sounds I have had many a problem with rear light clusters cause EML issues and I have seen grown men cry trying to fix em ! Think simple first. It may be when you select reverse you put your foot on the brake or the rear light cluster hasa poor earth when the 21wat reverse bulb comes on !

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Wed 27 Mar 2013 21:37

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - elekie&a/c doctor

Agrred as above.You need to do the voltage checks at the ecu connectors so that any wiring harness fault is taken into account as the engine moves.Engaging reverse alters the engine location slightly and could be putting stress on the wiring.I think your fault code is P0221.Also I doubt if the elm reader will work,as this car is not eobd compliant,as it is a diesel.hth

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Thu 4 Apr 2013 19:07

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - mw01908

Well I got my ELM reader and it does work. The codes I have (which keep coming back after clearing them) are: P220 TPS CIRCUIT B, and P120 TPS CIRCUIT A.

The reverse gear thing is a red herring. The problem occurs when I move the throttle pedal anything over about halfway depressed, thats when the revs drop and the car slows down despite me then putting my foot flat down, or as the ELM reader says 100% throttle. Eventually after a bit of kangerooing for 20 secs or so the car revs off and gets going but if I keep the foot flat it eventually kangeroos again and self varies the throttle. Interestingly the ELM reader only shows either 100% or 0% throttle no in between. This could be the limitation of the the reader or the app I'm not sure at this stage rather a sympthom of the fault.

I have unplugged the MAS, tested the TPS, I'm at a loss at what to try next. I can't get at the EGR but I wouldn't have thought it was that I can't see how it relates to the throttle. What is making the ECU think there's a problem with the TPS ??? puzzled...

Nearly had some people drive into the side of me at roundabouts this week!

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Sat 6 Apr 2013 23:56

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - mw01908

I'm pleased to report that the fault is now cured. For the benefit of anyone reading this board or has googled TPS on an Hdi, having similar problems, I'm posting the fix (for my car anyway)

It turned out to be a poor connection to the ECU. The white wire to the TPS was brittle and high resistance / intermittent further down from the TPS where it joins a cable running from the coolant level sensor. Stripped it back and soldered it for now but it could really do with a new part of that loom as the green wire was brittle as well. These wires have all the elements thrown at them plus all the vibration from the engine - its no wonder they go like this, plus pvc cable ages and does go brittle over time.

I cleared off the codes with the ELM reader and I have my car back! Its interesting that this one white wire being bad causes P220 and P120 TPS A and TPS B sensors. I suppose this is the generic nature of the codes thrown up? Anyway the lesson is test your TPS and don't over look the wiring. The warmer weather helps a bit too! My voltages on the TPS are still the same and posted earlier, so these looks like normal voltages for the 306 if anyone wondered what they should be.

I wonder how many garages would have replaced the TPS landing me with a £150 plus bill and still no nearer fixing the fault. One of the bolts on the TPS bracket is rusted through (the whole bolt moves with the nut) so it would have been a right job replacing it!

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Sun 7 Apr 2013 11:27

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - Simon

Excellent work, and it's nice to see a follow up solution to the original problem that you posted about.

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Wed 18 Dec 2013 11:19

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - char1

Hello,

I'm new to fixing old Peugeots but after getting a quote from the local garage to change the TPS (though by looking at the above posts this might not be the only fault! ), I thought now was a good time to get involved.

I have a Y reg 306 HDI with very similar symptoms; I checked with an ELM reader and recieved the same fault codes - P220 & P120.

I wanted to check the wiring to look for continuity faults but I dont have a wiring diagram for the car or a Haynes manual. I do have some experience of working with electronics - just not on cars! Would anyone be able to give me any advice on how/where to check the wiring to look for faults. Ideally any pics or diagrams to help visualise whats going on would be a big help.

Many thanks in advance.

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Wed 18 Dec 2013 13:59

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - Gibbo_Wirral

There are wiring diagrams here:

peugeot.mainspot.net/main.shtml

But, seriously, invest in a Haynes manual. You can pick up a second hand one for a fiver from Ebay.

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Wed 18 Dec 2013 21:10

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - char1

Thanks for your advice, I think you are right about getting a Haynes book. I think I'll order one on ebay. In the meantime does anyone know if there is a pdf version available? - I'd like to have a chance of getting the car fixed before christmas!

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Wed 18 Dec 2013 22:53

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - focussed

Haynes do an online manual for a 306- you buy a subscription to view the manual for a year for £20 or a lifetime for £25

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Wed 20 May 2015 22:32

Peugeot 306 Hdi - Throttle sensor circuit 2 fault, keeps coming back - vmturbo

If you do buy a Haynes take it with a LARGE grain of salt. For example their ideas of how to replace the brake light switch beggar belief as they tell you to remove the entire dashboard! WRONG! What one actually does is to remove the steering column nacelle (three Torx head screws). One can then drop the steering column by removing four nuts which are 13 mm AF. A bungee can be useful to hold the steering wheel out of the way. There is an oblong hole above where the steering column used to be. The hole is about 3" x 2" and the switch is inside it. Although the hole has sharp edges the switch can be pulled out by its wires as it simply pushes into a gripper rather like a towel gripper.

As to drive-by-wire systems, just remember that you are dealing with a computer. Now the number one golden rule with computers is RUBBISH IN = RUBBISH OUT. This means that if one has a faulty sensor giving a false signal THE COMPUTER WON'T KNOW!

A friend had this with a petrol powered 1.8 Vauxhall that failed its MOT for slightly out of spec Oxides Of Nitrogen. The engine was also running slightly lean but the car drove OK and returned good mpg. Two Lambda Sensors costing £90 each were bought but the NOX figure was the same. These days it is not possible to turn a blind eye over NOX being a fraction of a percent out of spec as the figures also go to VOSA. Next a drive-by-wire expert scanned the car but it was A1 with no faults stored! A new MAF was then purchased for another £90 and everything came right but £300 had now been spent! The problem is that the computer doesn't know whether the hot wire in the MAF is clean or whether dust and oil fumes have burnt onto it so its a case of rubbish-in = rubbish-out. Allegedly the hot wire can be cleaned by painting it with oven cleaner and leaving it overnight. In the morning one rinses-off the MAF and usually everything then works OK. Things are too complicated these days!

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