57 Yaris 1.4 D4D replacement ECU. Will I need to also buy the ignition & key to match the replacement ECU?

[stantheman1]

I still think you need to check the network with a scope to rule out any intermittent activity being transmitted.

Is there any sign of oxidisation on any of the connectors including fuse holders, relays, sensors, actuators etc? 

Are your fuel trims okay?

Have you tried using a different scan tool to measure the tps

I'm struggling to think of anything else other than the ecm/pcm.

 

[Cyclopse11]

If it was a TPS issue shouldn’t we be seeing code P1121? Have you thought about checking Throttle Position Sensor?

First start of the day I could go 5 or even 100 miles with no issue and no limp mode. Stop and on restart would be back in limp mode. More recently permanently stuck in limp with no EML or fault codes.

[aXeL_UK]

14 hours ago, stantheman1 said:

I still think you need to check the network with a scope to rule out any intermittent activity being transmitted.

Is there any sign of oxidisation on any of the connectors including fuse holders, relays, sensors, actuators etc? 

Are your fuel trims okay?

Have you tried using a different scan tool to measure the tps

I'm struggling to think of anything else other than the ecm/pcm.

 

I think you could well be right and, like Bob asked about scanner, I wonder if I should try a different one.  Just because it works with other cars ( it's a cheap multi-protocol Amazon job ), maybe it's not working reliably with the Yaris:
https://www.amazon.co.uk/NEXPEAK-Universal-Diagnostic-Scanner-Automotive/dp/B07CVVZ4YW/ref=sr_1_12?dchild=1&keywords=OBD+scanner&qid=1605260581&sr=8-12

Re. oxidation: The connectors wrt the harness itself, Toyota checked because they pointed out some damage to the old harness but I should check the fuses and relays.  Even just pulling, brushing and re-seating them might help. I'd like to check the CAN H and CAN L voltage wrt to ground but I read that it should be done with no systems running and I'm not sure ( correct me if I'm wrong ) if that's ever the case when there's power to the ignition.

Not occurred to me to check the long term and short term fuel trims, not sure my cheapo scanner can do it but will check.  BTW ( and I'm guessing here ) will that be particularly helpful? I only ask as I'm guessing they're narrow-band sensors which don't give much range or granularity as opposed to wide-band but then I don't really know fuel and trimming on the Yaris ( or diesels in general for that matter ).  Is it pretty much the same logic as for petrol cars?

[aXeL_UK]

14 hours ago, Cyclopse11 said:

If it was a TPS issue shouldn’t we be seeing code P1121? Have you thought about checking Throttle Position Sensor?

First start of the day I could go 5 or even 100 miles with no issue and no limp mode. Stop and on restart would be back in limp mode. More recently permanently stuck in limp with no EML or fault codes.

Hi Bob, I get the impression ( and please don't take offense! ) that you've skimmed the thread rather than read it.  Your query about the TPS has been pretty comprehensively answered already ( or not - did I just write it up badly? My apologies if I did ).

[aXeL_UK]

14 hours ago, Cyclopse11 said:

If it was a TPS issue shouldn’t we be seeing code P1121? Have you thought about checking Throttle Position Sensor?

First start of the day I could go 5 or even 100 miles with no issue and no limp mode. Stop and on restart would be back in limp mode. More recently permanently stuck in limp with no EML or fault codes.

BTW Rob, ignore what I said about the boost on your car, I missed something really obvious!!  If you have a CEL, the car will not let you go over 3000rpm for safety.  It's a feature.  Sorry, all my stuff about the turbo and whatnot is probably just fluff - my bad!

[stantheman1]

On 11/13/2020 at 9:56 AM, aXeL_UK said:

I think you could well be right and, like Bob asked about scanner, I wonder if I should try a different one.  Just because it works with other cars ( it's a cheap multi-protocol Amazon job ), maybe it's not working reliably with the Yaris:
https://www.amazon.co.uk/NEXPEAK-Universal-Diagnostic-Scanner-Automotive/dp/B07CVVZ4YW/ref=sr_1_12?dchild=1&keywords=OBD+scanner&qid=1605260581&sr=8-12

Re. oxidation: The connectors wrt the harness itself, Toyota checked because they pointed out some damage to the old harness but I should check the fuses and relays.  Even just pulling, brushing and re-seating them might help. I'd like to check the CAN H and CAN L voltage wrt to ground but I read that it should be done with no systems running and I'm not sure ( correct me if I'm wrong ) if that's ever the case when there's power to the ignition.

Not occurred to me to check the long term and short term fuel trims, not sure my cheapo scanner can do it but will check.  BTW ( and I'm guessing here ) will that be particularly helpful? I only ask as I'm guessing they're narrow-band sensors which don't give much range or granularity as opposed to wide-band but then I don't really know fuel and trimming on the Yaris ( or diesels in general for that matter ).  Is it pretty much the same logic as for petrol cars?

I'm not sure you'll be able to see the voltage with a multimeter the best tool would undoubtedly be an oscilloscope. EDIT: I tried this and I was wrong, you will be able to see a voltage between can H to -ve (approx. 2.65 volts) and can L to -ve (approx 2.15 volts) but this test wont tell you if any of the 'packets' are corrupt or dropping out occasionally.

With regards to the fuel trims I wanted to know if the ecm was reporting the values correctly if for instance they were out of range and not triggering a cel (this would then lead me to suspect the ecm) but I would imagine you'd be able to tell with the performance of the vehicle. 

The first thing I would do is try out an alterative scan tool, it's a shame you are too far away from me as I would love to see if I could help you solve this.

Fuel ratios are pretty much the same logic for petrol 14.7:1 and 14.5:1 for diesel engines.

[stantheman1]

On 11/13/2020 at 9:56 AM, aXeL_UK said:

I think you could well be right and, like Bob asked about scanner, I wonder if I should try a different one.  Just because it works with other cars ( it's a cheap multi-protocol Amazon job ), maybe it's not working reliably with the Yaris:
https://www.amazon.co.uk/NEXPEAK-Universal-Diagnostic-Scanner-Automotive/dp/B07CVVZ4YW/ref=sr_1_12?dchild=1&keywords=OBD+scanner&qid=1605260581&sr=8-12

Re. oxidation: The connectors wrt the harness itself, Toyota checked because they pointed out some damage to the old harness but I should check the fuses and relays.  Even just pulling, brushing and re-seating them might help. I'd like to check the CAN H and CAN L voltage wrt to ground but I read that it should be done with no systems running and I'm not sure ( correct me if I'm wrong ) if that's ever the case when there's power to the ignition.

Not occurred to me to check the long term and short term fuel trims, not sure my cheapo scanner can do it but will check.  BTW ( and I'm guessing here ) will that be particularly helpful? I only ask as I'm guessing they're narrow-band sensors which don't give much range or granularity as opposed to wide-band but then I don't really know fuel and trimming on the Yaris ( or diesels in general for that matter ).  Is it pretty much the same logic as for petrol cars?

Andrew please see my edited post re: voltage tests.

[aXeL_UK]

When the car is in limp mode and, frustratingly, it hasn't done it in three days, after months of being permanently in limp mode, the fuel economy is only about 2/3rds of what it should be and the power is down quite a bit but not intolerably, I guess because some sort of safe open loop fuel mode is being applied.  When the light is off, mpg is back to it's normal happy self and I can nudge ~600 miles from a tank.

Random factoid I've not mentioned before - ever since I bought the car I've been using Miller's diesel eco-max.  I'd been using it for years beforehand with my Mercs and I could get almost a thousand miles out of a tank on my SLK when using it ( with very careful driving ).  The Merc forums used to rave about the stuff but, I wonder if Toyota diesels don't like it since it effectively changes the combustion characteristics of the fuel.  What if it leans out the mixture and, ergo, gives the lambda sensors readings they don't like, e.g. too great a difference between the main sensor and the trim sensor.  Or maybe it's the occasional tank of cheap cr@ppy supermarket fuel I used to use until recently, e.g. Asda ( still with the millers though ). Maybe it can't burn that properly.

The other thing that's changed is how I drive the car.  When I first had the problem and the light came on more and more often before staying permanently on, I was doing ~250 motorway miles/week.  Now I rarely do more than town runs and have to make a point of doing longer drives now and again - I assume it needs to do a regeneration like my merc oil burners.

 

And maybe I'll have to do a week away in Yorkshire since every other country treats us like a leper colony.  TBH, even if I bought another car, I'd STILL want to know what was upsetting this one!

 

[stantheman1]

On 11/14/2020 at 10:40 AM, aXeL_UK said:

When the car is in limp mode and, frustratingly, it hasn't done it in three days, after months of being permanently in limp mode, the fuel economy is only about 2/3rds of what it should be and the power is down quite a bit but not intolerably, I guess because some sort of safe open loop fuel mode is being applied.  When the light is off, mpg is back to it's normal happy self and I can nudge ~600 miles from a tank.

Random factoid I've not mentioned before - ever since I bought the car I've been using Miller's diesel eco-max.  I'd been using it for years beforehand with my Mercs and I could get almost a thousand miles out of a tank on my SLK when using it ( with very careful driving ).  The Merc forums used to rave about the stuff but, I wonder if Toyota diesels don't like it since it effectively changes the combustion characteristics of the fuel.  What if it leans out the mixture and, ergo, gives the lambda sensors readings they don't like, e.g. too great a difference between the main sensor and the trim sensor.  Or maybe it's the occasional tank of cheap cr@ppy supermarket fuel I used to use until recently, e.g. Asda ( still with the millers though ). Maybe it can't burn that properly.

The other thing that's changed is how I drive the car.  When I first had the problem and the light came on more and more often before staying permanently on, I was doing ~250 motorway miles/week.  Now I rarely do more than town runs and have to make a point of doing longer drives now and again - I assume it needs to do a regeneration like my merc oil burners.

 

And maybe I'll have to do a week away in Yorkshire since every other country treats us like a leper colony.  TBH, even if I bought another car, I'd STILL want to know what was upsetting this one!

 

Andrew, did you manage to get it sorted?