[Techtone]

Hi sefiro,

But from my previous message, when in no start condition, I can see the ECU is switching, because when I tie the ECU injector output to a positive voltage with a 100R resistor, I can then see the ECU is switching. Surely this would indicate no 12V on the four injectors hot side?

P.S the fuel pump runs during crank in both start and no start conditions.

What do you think?

Thanks

Tony

 

[93celicaconv]

I think sefiro's guidance is very good. But the question Techtone asks is worthy to be checked. That question was: Therefore the issue is, when in no start condition, is: There must be no 12V at the hot side of all four injectors. Do you guys agree?

So please check for the presence of 12VDC on the hot side of at least one injector, Do so when the engine is capable of running, and when the engine will not start/run. Let us know what you find out with this test.

Regarding the ignition relay, per your diagram shown in post #39, it shows that relay along with the EFI relay in R/B No. 2. When I look at the Toyota Parts Diagrams for your VIN, it doesn't show an Ignition Relay in R/B No. 2. It does show the EFI Relay in there though. But, in fact, there is no relay named Ignition Relay in the parts information for that VIN. If your R/B No. 2 box cover shows a printed label on top of or under the cover, it would be great to see what that label looks like. If your shows an Ignition Relay, it would also be great to see what the part number is for that relay.

 

[sefiro]

Yes, there should be 12v on all injector wires. The 12v is then fed into the ECU where it is switched to ground to complete the circuit.

When you hooked up the scope on the working scenario, did you hook to a good ground? When the injector fired, the scope saw a voltage disturbance this the blip.

But in a no work scenario, you did not get a baseline voltage. You introduced a new power source and no telling what voltage blips (much smaller, probably coming from the voltage regulator on the alternator).

Thus my suggestion to chase the hot engine bay. I don't have a 6th Gen diagram, but I on the 5th Gen, the 12v power supply comes from the ignition switch.

 

[Techtone]

Hi 93celicaconv and sefiro, here's a picture of the fuse box interior.

And this is the inside of the fuse box cover:

Looking at the schematic:

I need to find relay IGN pin 5 or connector BA3 to check for 12V. However as 93celicaconv pointed out there is no ignition relay indicated in the fuse box!

93celicaconv do you have a schematic for my VIN JT164STL200125505 or any pointers as to which relay is switching 12V to the injector hot side? Or for that matter, where I might find connector BA3?

I think the relay and BA3 have to be prime suspects?

I could just hotwire 12V to the injectors hot side, but without knowing which relay and the location of connector BA3, I'm gonna have to take stuff apart to find the injector wiring...

A personal note, I live near a town popular with holiday makers. It made me laugh the other day, I was going through the McDonalds drive through and folk in the restaurant were taking pictures as we drove through! Guess she still turns heads. Lol.

Many thanks

Best regards

Tony

 

[93celicaconv]

I hope the view below is clear enough to view the parts diagram for relays on your car. There is no relay called Ignition Relay on it. Relay 9 (called Relay, Main) may be what the wiring diagram calls the IG Relay. You would have to take a look at it to see if it is a 5-pin relay. The circuit diagram for the relay may be printed on the side of the cover, instead of on the top. I don't have a wiring diagram for your specific vehicle. Your wiring diagram appears to be written for a Japan market Celica. I'm not sure your European market Celica was built electrically to be the same.

 

[93celicaconv]

In looking at that wiring diagram circuit sheet you posted for your Celica, I don't think that is correct for your car. I found a set of wiring diagrams for a European ST202, and I think what I will be showing you is for your car. The first attachment shows the Relay/Junction Box No. 2, which seems to match your photos perfectly. Note the relay labeled as E/G Main in your photo is labeled as Engine Main Relay in this diagram - so E/G would seem to mean Engine, which makes sense. The next two attachments is the wiring diagram for engine control on the 3S-GE ST202. As you can see, there is no ignition relay in the circuit providing constant 12VDC to your injectors. Only the IG2 pin of your ignition switch is used to provide 12VDC to your injectors. I think you need to verify if your IG2 pin on your ignition switch is working properly at all times, and check for your constant 12VDC between pin IG2 of the ignition switch and the delivery of the 12VDC at a fuel injector, especially at a time when the engine will not start, and see what that is telling you. NOTE: ECU connector "C" referenced in the last diagram - the injector wires going to the ECU, is exactly the same as connector "N" referenced in your photo of the connector used for the ECU - same pin locations - same setup.

 

[Techtone]

Hey 93 and sefiro, 93 thanks for the diagram.

She started at 7.00 a.m. to take my son to work. After that she has been crank no fire all day.

So today (my day off), I focused on Relay 9 the Main Relay.

After unplugging the relay here is what it looks like, please see pic below:

I can see 5 pins. i.e, a single pole double throw SPDT relay.

Here is the pin out stuff:

After re-inserting the relay, the symptoms kind of changed to crank, fire stall.

So to eliminate this relay as the suspect, I again unplugged the relay from the fuse box and inserted a piece of copper wire to short 30 and 87.

Looking at the jap wiring diagram and assuming the main relay is the IGN relay in the diagram below. This equates to shorting pin 4 and 5 on the IGN relay.

The results were, as soon as I inserted the link, with ignition off, the electric cooling fan started. On cranking the engine with the key the cooling fan stopped running and the crank, fire, stall condition persisted.

I'm not sure what this means, maybe I'm on the wrong relay? Or maybe the fault is around the BA3 connector. Oxidisation, thermal expansion, high resistance contact under load etc?

Any way, my family is telling me to sell the car and give up. But I refuse.

The way it is looking to me now is, the only way to get closer to cracking this nut is:

'I have to measure the signal at the injectors'

I really appreciate you guys help getting to the bottom of this.

Please can you guys advise me of the procedure, to expose the injector connectors for measurement and scrutiny.

I keep telling myself, in crank no fire there is no output measured on the scope unless I pull the ECU injector out put high with a resistor. Then the ECU can be seen switching. This means the ECU working. Sorry to repeat myself. But occam's razor says this means no 12V on the injector hot side. Or 12V to begin, when fire then none when stall after fire.

Victory shall be ours!

I have to measure 12V it at the injector connectors hot side. Wish I knew where connector BA 3 is!

Guys how to get to the injector connectors please?

Thanks

Tony

 

[93celicaconv]

I guess you did not read my posts prior to your update just moments ago. Oh well. That relay is your engine main relay. It has nothing to do with your fuel injectors. And from what I can tell, your Japan wiring diagram is not for your specific European ST202. Meaning you don't have a relay between your ignition switch and the fuel injectors. Maybe read what I previously posted?

 

[Techtone]

Hi 93celicaconv,

Yes, sorry I somehow seem to have missed your post #46. Thanks for the new information and the wiring diagram, which is like gold dust! Good to know there is no relay switching the 12V for the injector hotside.

I will test the ignition switch IG2 for 12V as suggested.

Many thanks for researching this for me.

I will come back with the results.

Tony

 

[Techtone]

Yes, there should be 12v on all injector wires. The 12v is then fed into the ECU where it is switched to ground to complete the circuit.

When you hooked up the scope on the working scenario, did you hook to a good ground? When the injector fired, the scope saw a voltage disturbance this the blip.

But in a no work scenario, you did not get a baseline voltage. You introduced a new power source and no telling what voltage blips (much smaller, probably coming from the voltage regulator on the alternator).

Thus my suggestion to chase the hot engine bay. I don't have a 6th Gen diagram, but I on the 5th Gen, the 12v power supply comes from the ignition switch.

Hi sefiro,

I connected the scope ground to the metal plate that the ECU is bolted to and which is bolted to the car chassis.

When in no start condition, I hooked up a 9V PP3 battery to ground and the 9V with a 100R resistor to the ECU injector output and could then see the ECU was switching.

I am going to get to testing the ignition switch next.

Thanks for your input.

Ton

 

[93celicaconv]

Just remember that your switch may test OK. If it does, you likely have a wiring fault between the ignition switch and the injectors.

Also, your switch may test bad, but it may not be the switch. You would need to test the incoming wiring circuit to IG2 to see if it is the source of the drop in voltage. You fuse in the circuit going to IG2 may be problematic. You always need to find what is furthest upstream (where the problem first begins and just upstream it is always good). Takes time and patience!

 

[Techtone]

Hi 93celicaconv, this weekend, I will, for sure checking the ignition switch and wiring out. I'm not much of a mechanic, but I been doing electronics since I was 12, back in 1975 lol. So I'm reckoning, with the help of you guys on this forum, I can track this issue down.

I will post my findings here.

Many thanks again for your time and info, insight and moral support, I really appreciate it.

Tony

 

[sefiro]

Jumping back in (had been reffing soccer for 5 days straight - rehydrating at the local Fox & Hound)

Ditto on 93's recommendation to check ig2 output on the ignition switch. I went back thru and looked at your scope readings. When you added the 9v battery, you are sending current back thru the system and may have measured other extraneous activities. Since the system was likely not getting 12v everywhere, the 9v might be partially activating circuits with weird signal outputs. (Ie, the igniter might be trying to drop current to the coil. Not sure what RPMs where being used on each test (the fail test is likely a lower rpm than good test. Factoring that in, the blips on the failed test would be closer together if adjusted for rpm speed - thus the theory that the blips are 4x the normal injector firing which would be 1 blip for every 4 igniter blips

BTW. Found the manual on the Internet archive.

Toyota Celica Electrical Wiring Diagram ST20_ / AT200 Series (Oct. 1993) : Toyota : Free Download, Borrow, and Streaming : Internet Archive

PDF originally posted to MWP's Toyota Celica GT4 Documents & Media

archive.org

 

[Techtone]

Hi sefiro,

I hope you enjoyed your soccer reffing break and have recovered from the rehydration process!

About the scope readings, when in start and running the scope picture was taken with the engine idling and shows a period of 160mS between pulses which is about 6Hz. Times by 60 for RPM = 360, which sounds too low? When in the no start condition with the 9V battery attached, to see in the ECU injector output was switching, the RPM was just how fast the starter motor could turn the engine over.

When in When in the no start condition with the 9V battery attached, the pulses seem closer together, between 50mS and 100mS which would equate to 1200RPM to 600RPM!

Perhaps I should revisit the ECU injector outputs and perhaps add four LEDs with resistors to be able to see all four injector signals are present and operating in sequence?

On 93's recommendation to check ig2 output on the ignition switch. I didn't make too much progress, but will post my findings in a minute, in the next post.

Many thanks for finding the manual on the Internet Archive. I have joined and downloaded the document and will study it.

Cheers

Tony

 

[Techtone]

Hi 93celicaconv and sefiro,

I disassembled the dash in search of ignition connection IG2.

Here's what I found, some sort of ignition ring sensor, which I could not find on 93celicaconv's Engine Control diagrams in post #46. I was unable to make a measurement of the ignition ring and am unsure what it does, some sort of sensor to detect a magnet in the barrel of the lock?

There is a switch screwed to the underside of the ignition lock. This measured open circuit and 1.7R when pressed.

The other connector I found coming from the ignition lock is pictured below:

This connector has 3 wires. The white wire measured at 12V with key in or out. The black wire measured 7R to ground. The red wire measured 0V with key out. On inserting the key the red wire measured 4.89V for around 10 seconds, after which it reverted back to 0V.

When the key is turned to start the car the red wire measured 4.89V.

All measurements were made in the no start condition.

I was unable to locate IG2 as none of my wire colours seem to match up with the Engine Control diagrams in post #46.

So I'm none the wiser at the moment.

I went out to check if the 4.89V stays when she is running, she started, I was not able to measure the 4.89V because I don't think my probe was connecting. I stopped her after 30 seconds. Now she is in the no start condition, with a cold engine. It's about 10C outside today.

It feels like my symptoms are changing, not sure if it is because I have disturbed the fault area or just that I have never really tried start, stop and restart while still cold.

It's just really weird, how can I have this issue, when once started she never cuts out or stalls? If it were a bad connection on the injectors, surely she wound cut out / stall while running?

Anyway a few hours later after she was crank, fire, stall and she is just crank no fire now.

Looking through sefiro's 'Toyota - AT202-ST204 - Electrical Wiring Diagram (EWD198Y).pdf', page 10 shows fuse AM2 supplies to hot end of the injectors and the ignitor. I have confirmed I have 12V on both ends of the fuse with the key out and when cranking.

I will study 93celicaconv's diagram from post #4 again and also look at sefiro's 'Toyota - AT202-ST204 - Electrical Wiring Diagram (EWD198Y).pdf' which I downloaded from the Internet Archive.

Hmmmm....

 

[93celicaconv]

Hi 93celicaconv and sefiro,

I disassembled the dash in search of ignition connection IG2.

Here's what I found, some sort of ignition ring sensor, which I could not find on 93celicaconv's Engine Control diagrams in post #46. I was unable to make a measurement of the ignition ring and am unsure what it does, some sort of sensor to detect a magnet in the barrel of the lock?

There is a switch screwed to the underside of the ignition lock. This measured open circuit and 1.7R when pressed.

View attachment 34999

I previously responded thinking this was an ignition cylinder illumination ring. But I see that, for models ordered with anti-theft, there was a coil used with a transponder key. The coil in the parts diagram below seems to match the geometry of the item in the photo that you called the ignition sensor ring. That appears to be correct. Which now brings up the subject if the coil, the transponder key transmitter, the amplifier, or the transponder computer are failing. Does the transponder key transmitter require a battery to function?

 

[93celicaconv]

In your photo, the item you labeled "Measures 1.7R when pressed" is your key interlock solenoid. What it does is it prevents you from being able to turn your ignition key to LOCK position (to remove your key from the ignition cylinder) if your transmission shifter is not in the PARK position. It may play a role in other aspects of the transmission shifter as well. It has nothing to do with engine control.

 

[93celicaconv]

The attached photo is for a complete 6th Gen Celica ignition switch and bracket assembly. There is a red arrow pointing to a wiring harness connector. What we need to see is the wiring harness connector and wire colors going into that connector from your car. A second photo with a red arrow shows a closeup of this connector. This is the ignition switch for your car. This is where IG1 & IG2 and ST and other wires come into play. You haven't shown us the wiring harness connector and wires that plug into this spot yet. Please post a photo of this from your car. The third photo is one you posted, with a red arrow pointing to the wiring harness connector for the ignition switch that we need to see closer with a much better view of the wire colors in each pin of that connector. The fourth photo shows you what your ignition switch wiring harness connector looks like. And the fifth photo shows what the wire colors should be at each pin of that I12 wiring harness connector.

 

[Techtone]

I previously responded thinking this was an ignition cylinder illumination ring. But I see that, for models ordered with anti-theft, there was a coil used with a transponder key. The coil in the parts diagram below seems to match the geometry of the item in the photo that you called the ignition sensor ring. That appears to be correct. Which now brings up the subject if the coil, the transponder key transmitter, the amplifier, or the transponder computer are failing. Does the transponder key transmitter require a battery to function?
View attachment 35002

Hi 93celicaconv, thanks for your message and research. To answer your question, yes my key comes with a fob for the alarm. It takes a CR2032 or CR2025 battery:

My keys look like this:

Thanks

Tony

 

[93celicaconv]

Your response above doesn't address the question I had for what you replied to. Maybe we need to understand a couple of things now:

1. Your key fob has nothing to do with the transponder key coil brought up in post #56
2. Your key (a transponder key) is what is coded to the transponder key coil (which you called an ignition ring in your photo in post #55. This group is part of an anti-theft option you must have on your car, as you clearly have the transponder key coil in your photo, a part of this system.
3. Your key fob is part of the TVSS (Toyota Vehicle Security System), which is independent of your anti-theft system. Your key fob works with TVSS to remotely lock & unlock your doors. When activated, it will prevent the starter from engaging with the engine flywheel, preventing the engine from turning over when attempting to start. I will also trigger the horn to start beeping.

All these things complicate diagnosis on what is causing your symptoms. I'll let you read through some of the recent posts trying to help you - perhaps your responses to those questions asked will help narrow things done a bit.