OBD Wiring Schematics

[AV3]

Hello

Would anyone be able to tell me where I could find a wiring schematic of the OBD components on a 2000 Avensis. I have  looked through the Haynes manual several times but it does not seem to cover any of the components. Have I not looked hard enough 

 

Thanks for your time

[oldcodger]

Looking in my earlier petrol Avensis  Haynes manual it does not show them either, they are clearly incomplete diagrams.

My book does show pictures of the location of the first 2 sensor, but the third , assume thats the diesel model only.

Are you getting the engine check light on  or are these readings possibly old events.

You can clear the ECU error codes by disconnecting the Battery or shorting pins 4 and 13 on the obd socket, then turning the ignition on.

You can view /buy time on Toyotas site to see various diagrams, though never used it myself.

https://techinfo.toyota.com/techInfoPortal/appmanager/t3/ti?_nfpb=true&_pageLabel=ti_home_page&contextType=external&username=string&password=sercure_string&challenge_url=https%3A%2F%2Ftechinfo.toyota.com%2FtechInfoPortal%2Flogin%2Ftechinfo&request_id=2481699692878023539&authn_try_count=0&locale=en_US&resource_url=https%3A%2F%2Ftechinfo.toyota.com%2F

 

 

[Konrad C]

I have some info on the the older pre face-lift Avensis which included the OBD socket. 07_DIAGNOSTICS.pdf
What do you need to know and what are you trying to do?

 

[Konrad C]

More info I found on the net - http://pinoutguide.com/CarElectronics/Toyota_lexus_obd2_diagnostic_pinout.shtml

The following is for face-lift Avensis which is OBD2 compliant - the earlier Avensis is not. I used pins 4 and 13 to get the codes from the EML/ABS/SRS lights, Morse code style.

Haynes never did diagnostic on the Avensis. Most the things I learnt are from this forum and the internet in general. 

[Konrad C]

I have the bigger file 22MB which covers more info. 7_DIAGNOSTICS.pdf
Hope it uploads.

[AV3]

On 11/08/2017 at 8:40 PM, oldcodger said:

Looking in my earlier petrol Avensis  Haynes manual it does not show them either, they are clearly incomplete diagrams.

My book does show pictures of the location of the first 2 sensor, but the third , assume thats the diesel model only.

Are you getting the engine check light on  or are these readings possibly old events.

You can clear the ECU error codes by disconnecting the battery or shorting pins 4 and 13 on the obd socket, then turning the ignition on.

You can view /buy time on Toyotas site to see various diagrams, though never used it myself.

https://techinfo.toyota.com/techInfoPortal/appmanager/t3/ti?_nfpb=true&_pageLabel=ti_home_page&contextType=external&username=string&password=sercure_string&challenge_url=https%3A%2F%2Ftechinfo.toyota.com%2FtechInfoPortal%2Flogin%2Ftechinfo&request_id=2481699692878023539&authn_try_count=0&locale=en_US&resource_url=https%3A%2F%2Ftechinfo.toyota.com%2F

Thanks OC, I will look into that link. I dont have an illuminated CEL, the car was hesitating under acceleration on the motorway and smoothed out when I lifted of the pedal so I pulled the codes (the ones I posted) reset drove again and pulled the same codes. I thought it indicated a vaccumm leak but I cannot see anything obvious though, I have not pressure tested as I dont have equipment to do so, I might be able to rig up a cheap pressure sprayer if needs must.  

I purchased a new intake temperature sensor as it was under £10 and an easy swap, so that should be here some time next week and hopefully it will clear one of the faults, if not I suspect it may be a common wiring fault shared by the three componants. Hence trying to get ahead of myself and better understand what is connected where just in case I need to know.

  "My book does show pictures of the location of the first 2 sensor, but the third , assume thats the diesel model only." 

Thats exactly what I thought reading the description, however I have a 1.8 petrol leanburn. I found out one of the sensors sits on the bulkhead and the other below the intake manifold, so I guess I am hoping its something as simple as a ground fault because the price of those parts is prohibitive and the one under the manifold will be time consuming. 

Thanks again OC for your taking the time to reply, very much appreciated.

[AV3]

On 12/08/2017 at 10:19 AM, Konrad C said:

I have some info on the the older pre face-lift Avensis which included the OBD socket. 07_DIAGNOSTICS.pdf
What do you need to know and what are you trying to do?

Hello Konrad, thank you for the replys, I have downloaded both the files you linked and they are incedibly helpful.

I have three stored fault codes and need to test the operation of at least two components with a multimeter.

I cant back probe the components with a multimeter because Toyo wiring is weatherproofed (very nicely), and one of the components is not practicle to access without a fair bit of work. I could splice a cable to get a reading, but it would be preferable If I could trace wires back to a connection that is more convenient to access. I cant visualy trace the wires without unwiding the loom, so I want to build up a mental picture of the OBD which I can work with.

[AV3]

17 hours ago, Konrad C said:

More info I found on the net - http://pinoutguide.com/CarElectronics/Toyota_lexus_obd2_diagnostic_pinout.shtml

The following is for face-lift Avensis which is OBD2 compliant - the earlier Avensis is not. I used pins 4 and 13 to get the codes from the EML/ABS/SRS lights, Morse code style.

Haynes never did diagnostic on the Avensis. Most the things I learnt are from this forum and the internet in general. 

Thanks again Konrad, my google-fu is lacking, the link is very helpful. Its weird, I have an OBD2 connector but I cant get a connection to an OBD2 compliant reader. Im just glad I can use the pin jumper to get the flash codes or I wouldnt have a clue where to start.

[Konrad C]

Hi Evan. The issue with the leanburn and other pre-face lift Avensis, is that they are not OBD2 compliant. The OBD socket is the same 16 pin but needs a scanner that reads older Toyota codes. Because it it is so simple to use the jumper wire to do the same thing, that is what I did during my ownership of the Avensis. I wonder if the Toyota TIS works with the older Avensis?
The PDF's I have, I got them a few years back. Some are very large and I did not know if the files could be posted. There are even larger files. 
Talking of emissions and OBD standard, correct me if I am wrong - later OBD2 cars have a pre and post cat sensors, which measure the emissions. That means if something is not right, the EML will illuminate. The older cars with only one O2/leanburn sensor don't have this, so less accurate - cars can pass the emissions even with EML! I wonder if any OBD2 cars have failed emissions without showing an EML?    

[AV3]

On 13/08/2017 at 0:40 PM, Konrad C said:

Talking of emissions and OBD standard, correct me if I am wrong - later OBD2 cars have a pre and post cat sensors, which measure the emissions. That means if something is not right, the EML will illuminate. The older cars with only one O2/leanburn sensor don't have this, so less accurate - cars can pass the emissions even with EML! I wonder if any OBD2 cars have failed emissions without showing an EML?    

Hello Konrad, sorry for the delay in getting back to you, the question got me thinking for sure and while I dont have a concrete answer, I guess it depends on the cause of the symptoms everything being relative. I will be sure to let you know how everything turns out. 

Thanks again

Evan

[AV3]

KonradC just wanted to say thanks again for uploading those documents, they helped me a great deal in beginning to understand the OBD and enabled me to start testing for faults with a multimeter.

To update this thread, I think I need a new ECU after following the testing procedures laid out in the documents KonradC uploaded.

Initially I changed the temp sensor and reset the ECU by removing the Battery negative terminal, on reconnecting the terminal and turning the ignition to on without having started the engine all three codes were still in memory without a CEL showing.

The voltage on the harness for the intake temperature sensor was 5.01v measured at the sensor end with the sensor disconnected.

I tested resistance on the temp sensor which gave 1.64k at 20 degrees Celsius which seems to be within the curve on the documentation. The voltage measured on the ECU pins THA to E2 ground was 5.01v without the sensor connected and 1.95v at 20 degrees Celsius with the sensor connected. ( I need to check this voltage drop matches the measured resistance on the sensor, I was unable to get a resistance reading.)

The voltage on the harness for the pressure sensor was 5.01v measured at the sensor end with the sensor disconnected for both VC to ground and PIM to ground

The pressure sensor at the ECU pins with the sensor connected gave 5.01v at VC to E2 ground and 3.62v at PIM to E2 ground. At this point the documentation suggest that I should replace the ECU as the sensors are within spec and E2 ground is good.

Having looked through the documentation, the pressure sensor fault should have triggered a CEL, and one of the sensor faults is for a component that is not fitted to my car. I mistook the (34 Turbocharger Pressure signal.) fault code for the Idle control valve, mainly because I am an idiot, I was trying to force fit the data to what I understood at the time I worked under the presumption that the fault code must be for a component on the car and that Toyota had just used a ridiculous naming convention.:). I am still intrigued as to how this fault code could even be triggered and held in memory.

There is a further interesting observation that might not be of consequence, fault codes are flashed out of numerical sequence starting 3-1-16-16-2-3-3-4-3-1-16-16 looping back to 3...and it is the seatbelt light which flashes the codes. From what I have read and watched, I expected the CEL to flash the codes and that they should be should be stored and flashed in numerical sequence.

The pressure sensor fault means the ignition timing cannot be advanced which I believe accounts for the hesitation under acceleration and sluggish response, in addition the intake temp value is fixed at 20C. The car can still be driven but I am concerned continued use in its present condition will cause damage.

I will start a new thread regarding an ECU swap.

Thanks again for your help

[oldcodger]

Hi,

Have you considered a proper diagnostic check to try and identify the actual problem  and check the ecu ?

The trouble with secondhand and really cheap sensors etc  is you never know if you are introducing more problems than they cure.

 

 

[AV3]

7 hours ago, oldcodger said:

Hi,

Have you considered a proper diagnostic check to try and identify the actual problem  and check the ecu ?

The trouble with secondhand and really cheap sensors etc  is you never know if you are introducing more problems than they cure.

Hi OC

To be honest I had not thought to take the car for a diagnostics check, I did not think they were able to capture any more data than was available using the jumper pin method given the car is not OBDII.

From my point of view the sensors are just variable resistors that adjust the voltage returning to the ECU which the ECU then interprets using a stored table to adjust another voltage on its output side, such as duration of signal for injector pulse. If a variable resistor is measured to be within operating specifications it is working cheap or not. I followed Toyota's own guidelines for testing the components and harness both of which are good, so that leaves the ECU. In addition to the fault codes stored, the ECU is not illuminating the CEL for one of the codes which it should and holds a code for a part not fitted to the car.

I figure I can get a replacement ECU second hand for less than the cost of a diagnostic, which depending on the result of the diagnostic I might have to purchase anyway. Using the replacement ECU I can see if this clears the reported fault codes, though I expect I wont be able to start the car due to the transponder. If the replacement ECU does not clear the fault codes then I know the fault lies else where, it still works out cheaper than a professional diagnostic.

A new ECU without the cost of programming exceeds the value of the car or a newer used car. I would really like to be in the position where I could pass this off to the proffesionals or buy the best parts I can to remove concern about quality, however I am not in that place and need to work with what little room for manouvre I have.  

Thanks again for your help, best regards

Evan

 

[Konrad C]

Hi AV3. 

The professional diagnostics guys might have equipment that can check the pre OBD2 cars including the Avensis. Just ask. Techstream with the mini VCI cable should work! 
I found this - http://www.dtdauto.com/Download/GUIDEBOOK_EFISCAN_1.5_E.pdf  It lists OBD1, the 7A-FE engine and also cars before and after the Avensis you have.

This should help you decide. 

Konrad.

[AV3]

On 03/09/2017 at 9:20 PM, Konrad C said:

Hi AV3. 

The professional diagnostics guys might have equipment that can check the pre OBD2 cars including the Avensis. Just ask. Techstream with the mini VCI cable should work! 
I found this - http://www.dtdauto.com/Download/GUIDEBOOK_EFISCAN_1.5_E.pdf  It lists OBD1, the 7A-FE engine and also cars before and after the Avensis you have.

This should help you decide. 

Konrad.

I caved in and ordered a cable from fleabay, I have an old laptop I can install the software on.

It would be silly of me to ignore an opportunity to better understand the problem before acting. 

Thanks OC, thanks Konrad, I really do appreciate the time you have both taken to help me. I will be sure to update the thread and let you know what was possible with Techstream, I dont think the cable will be here until the end of next week. 

Best regards Evan

[AV3]

Just to update this thread, I received my cable and after a week of messing around trying to load drivers ordered a second cable and confirmed the first cable was DOA. After getting TS up and running on the laptop I was unable to connect to the car using the DLC3 port.

After that I brought a second hand ECU and reprogrammed the transponder chip to accept my existing keys which I managed to finish last night. I swapped out the ECU this afternoon and while the car starts no problem the error codes are still there. I am at a loss and tempted to get a diagnostic test.

My concern is that I will have to pay for a test that will result in a mechanic scratching their head and saying "Yeh its a bit of a funny one mate, not sure what's going on there". The Toyota documentation says that 31 Air Flow Meter signal (Vacuum Sensor signal) should activate the Check Engine Light.

I am going to get some multi-metre test probe clips so I can check the vacuum sensor signal sensor while the car is running, though from what I have read this sensor failing should not also cause an intake temp sensor fault code. I cant begin to do anything about the .34 Turbocharger Pressure signal code seeing as my engine is a non turbo lean-burn.