P1121 Code On 2002 Yaris D4D - What To Fix?

[nigelp]

Hi folks,

I've just got a P1121 code after going into limp mode. It's happened a couple of times before, and the limp mode usually clears after I switch off the engine for a few minutes, but now I really need to get it fixed.

According to the code book, it's an 'Accelerator Pedal Position Sensor Range' problem, which is something to do with the pedal and/or throttle body, apparently.

I've been told that I probably need to change the throttle body sensor, or pedal assembly or both or something? Obviously I would like to avoid spending too much money if possible. Can anyone help? Is it easy to do or hard?

(and does anyone know any dependable Toyota diesel experts in London?)

Thanks.

[Devon Aygo]

P1121 Specifically relates to a fault within the the throttle pedal sensor, wiring harness or engine ECU basically the ECU has picked up a signal that is not within normal perameters and puts the car in to limp mode for safety sake.

The diagnostics requires a diagnostic machine able to display the reading output from the throttle pedal sensor as it is operated, measuring resistances across wiring harnesses and pinning out ECU terminals, so you will need either a Toyota dealer or an auto electrician with a very high end diagnostic machine.

[nigelp]

Shoot that sounds expensive. But thanks for the tip. As a matter of interest, how hard is it to find an intermittent fault like this with electronics, do you know?

[MikeSh]

Before shelling out for a pro-diagnostic it might be worth finding the connectors between the pedal and ECU (at a minimum I'd expect there to be one at/near the pedal position sensor and probably a big one with multi-inputs on the ECU) and unplug and replug a few times - Battery disconnected first. If it is just a poor contact that should sort it.

If that doesn't fix it then depending on costs (of pro-diag vs new part) I'd consider replacing the pedal sensor next as that shouldn't be a hugely difficult job. It's an old car (if it's the 2002 in your sig) and that bit is mechanical and has probably been up and down a fair few times by now.

[MikeSh]

how hard is it to find an intermittent fault like this with electronics, do you know?

Horrible. Especially as you can't wield a multimeter while driving :)

[nigelp]

how hard is it to find an intermittent fault like this with electronics, do you know?

Horrible. Especially as you can't wield a multimeter while driving :)

Heh. :)

[Madasafish]

You can always rig a multimeter with extra cable so a passenger can read it when you are driving ... been there, done that....It helps in reality if the passenger knows what they are doing. - mine did not, so she drove and I passengered...:-)

[nigelp]

You can always rig a multimeter with extra cable so a passenger can read it when you are driving ... been there, done that....It helps in reality if the passenger knows what they are doing. - mine did not, so she drove and I passengered...:-)

Hah, thanks Madasafish, but that assume that one of us knows what we're doing with a multimeter. Unfortunately I don't, so we'd both be as much use as a chocolate teapot.

[julieW]

Hi TOC people,

Just joined because I have a p1121 fault code exhibiting exactly the same symptoms as nigelp. Spoken to garage about new sensor and have been quoted £300.82 + vat for pedal assembly as a sensor not available separately. Have tried looking online for spares or second hand parts but no luck yet. Part no. for pedal *****. is 78010-52010. Any ideas please ?

[FROSTYBALLS]

Hello Julie - welcome to Toyota Owners Club

Could send Parts King a personal message, giving details of your car and what you want - may get some discount on the part you're looking for.

For Parts King, go to the Community page, scroll down to Sponsor's Corner and Lindop Toyota.

[nigelp]

julieW, in the end a electrical expert friend of mine took off the accelerator box (pedal assembly), took it apart a little and sprayed some high quality electrical contact cleaner spray into it. Wiggled it around for a while, cleaned a few contacts, put it back into place and the whole thing has been working perfectly (touch wood) ever since. Maybe that might be worth doing before splashing the cash? It seesm that these things get a bit dirty over the years (he found a tiny dead spider in there somewhere too. :)

[julieW]

Thanks Nigel, definitely worth a try, couldn't believe price, similar for another model was £38 !!

[nigelp]

Yes Julie, had that same issue with the price of a rear wheel bearing, which was 10x other cars. But found a much cheaper one by Continental on eBay. It pays to hunt around. Still love the car though. :)

[julieW]

Nigelp, funny you should mention rear wheel bearings, just got clobbered for two for MOT, so having just spent £500 to get through my test I am loathe to spend more on outrageously overpriced parts ! Did you happen to find a part number on the sensor ??

[nigelp]

Julie, did you mean part number on the sensor or on the wheel bearing? I didn't buy an accelerator sensor.

[julieW]

Hi Nigel, I meant the sensor, just wondered whether you or your electrician friend found a part number or code on the sensor when you cleaned it ?? I have had a couple of replies from suppliers for a used part but don't have a part number to confirm correct item. Hoping to get it looked at/cleaned tomorrow so fingers crossed !

[nigelp]

Julie, sorry we didn't look at the number. See how you go with cleaning. You should be able to find the exact sensor you need by marrying up the reg number with a search on Eurocarparts which gives you a type/catalogue number, then you can do a search on eBay which is what I did for the wheel bearing.

[julieW]

Nigel, OK thanks very much

[MrG1981]

Mine has just thrown this code up (twice in one journey) but it was a very wet journey, though the problem seemed to come on at points of steady pace. I've never ever experienced limp home mode before. My other car is a 1986 Fiesta! 

But have g only ever owned an old car with no electrics first instinct was "bloody waters got in, where's me can of damp start". Before realising I didn't own such stuff because it's a diesel and didn't consider I'd need it! 

Still think it's water in a connection but thankfully I work for a company that makes automotive position sensors so will get them on some test gear tomorrow. 

Can anyone Pont me in the position of the throttle assembly on the engine? It's my first diesel car! 

[nigelp]

9 hours ago, MrG1981 said:

Mine has just thrown this code up (twice in one journey) but it was a very wet journey, though the problem seemed to come on at points of steady pace. I've never ever experienced limp home mode before. My other car is a 1986 Fiesta! 

But have g only ever owned an old car with no electrics first instinct was "!Removed! waters got in, where's me can of damp start". Before realising I didn't own such stuff because it's a diesel and didn't consider I'd need it! 

Still think it's water in a connection but thankfully I work for a company that makes automotive position sensors so will get them on some test gear tomorrow. 

Can anyone Pont me in the position of the throttle assembly on the engine? It's my first diesel car! 

The throttle position sensor is under the throttle inside the car (at least it is on my vehicle). It's a small black box with a spring and lever on it. In the end I had to buy a complete replacement throttle from Japan through a 3rd party supplier on eBay - shar.soli - (Toyota Sienta part 78010-52050) which still cost quite a lot, but it was the only way to cure the problem completely (and Toyota here wanted an absolute fortune for a replacement throttle). Good luck.

[Andre2008!]

Did anyone happen to find a reliable supplier with this part in stock, the same issue has just happened to my toyota, but I am unable to source it anywhere. Any help appreciated.

[YarisManEire]

Same problem on my new 2004 Yaris TSpirit D4D originally from UK. Just nearing 2000 miles up by me and have been having this problem intermittently for the last 800 or 900 miles. Major panic at first limp mode, I hought the injector pump or something major was gone. Luckily I was only a couple of hundred metres from base so limped home. Then trying to find the throttle cable only to discover there was none. 

Interesting to read about cleaning it with high quality electrical contact cleaner. I took out the throttle assembly this morning with the same thought about spiders small insects etc. I didn't have the electrical contact cleaner though. The potentiometer part of it looked sealed so didn't open that, or didn't try to adjust the potentiometer part of it. No major dirt on the outside of it. But I did vacuum what I could see, a little bit of dust and photographed the part numbers before putting the throttle back in. 

Later got a trusted mechanic to plug in a computer to confirm that it was the P1121 code. He also checked the movement of the throttle while connected to the obd2 computer and found the movement to be laggy and stiff. 

Now on the hunt for a replacement throttle pedal. Have some leads including new. A bit iffy about replacing secondhand given how important the throttle is.

Nice to see that this seems to be a common problem. 

[julieW]

Hi Seamus, thanks to Nigelp, the "fix" for my problem was disconnecting the plug on the pedal sensor and spraying the contacts both sides with wd40 or contact cleaner, be generous to flush out any dirt/debris and use cotton buds to clean if necessary. Leave to dry (wd40) if possible and plug back together, simples ! This was after the garage had suggested spending loads of money on a new accelerator pedal assembly (cannot get sensor separately) or, if that didn't work, a new ecu !!  Best of luck, Julie

[YarisManEire]

Thanks Julie. The problem hasn't struck since, despite a good bit of driving. Maybe the vacuum did something, or taking out the pedal and turning it upside down. 

[YarisManEire]

Issue came back with a vengeance after about a week.

Bit the bullet and acquired and fitted complete new throttle Pedal assembly. Also bought a cheap wireless OBD2 code reader. And tested and replaced the Battery which may have been the original Battery that came with the car. It was a Yuasa Battery. Replaced with a Bosch. 

So far this Yaris bangeronomic has needed a few quid. But at 220k miles you'd expect a few things to go wrong only hopefully not too much. 

My last Yaris 2000 -1 litre vvti seemed to be almost indestructible except for some rust issues. Retired for me at 240k miles but still going strong for it's new owner.