ECU Schematic for 1G Eclipse?

Posting again - evidently there are not a lot of these old 1G's out there.

Anyway.... my problem is the Check Engine light does not illuminate. The bulb and all circuits external to the ECU board are fine. The board is also good between the 12VDC into the board from the bulb and ground. I suspect the trouble is the transistor or associated capacitor, but the board has been worked on before and the markings on these parts are no longer readable.

So, without a schematic, I wonder if someone more familiar with this type of circuit could guess at a possible replacement for the transistor and capacitor.

I know this is not the "proper" way to do it, but the alternative is buying a new ECU - several hundred $$. So I'd like to try a few things that mght have a chance of working before doing that.

Here's the only schematic I can find that shows the transisitor and resistor on the board, but no info as to what the parts are. Also, can't find what is connected to the base. I can swap out the parts from the component side of the board OK, but can't trace the leads or it would likely damage something else on the baord -- due to the condition of the board. I just need the car to pass smog so I can continue restoring the car, but dont want to put a lot of money into anything until I'm sure the car is worth it.

Thanks in advance!

Bob

Thanks.

Bob

The +12 from the Check Engine LED (pin 64 at MPI control unit on this)....

... connects to this component unfamiliar to me. Anyone recognize it? It is labeled CM104. Can't get a clear view for a photo. Rough sketch....

Most connections on this part of the board are underneath parts I can't get to. No markings on it that I can see. There are 7 of these on the board, all packed close together under a metal piece which is not practical to remove.

Anyway.... my problem is the Check Engine light does not illuminate. The bulb and all circuits external to the ECU board are fine. The board is also good between the 12VDC into the board from the bulb and ground. I suspect the trouble is the transistor or associated capacitor, but the board has been worked on before and the markings on these parts are no longer readable.

So, without a schematic, I wonder if someone more familiar with this type of circuit could guess at a possible replacement for the transistor and capacitor.

I know this is not the "proper" way to do it, but the alternative is buying a new ECU - several hundred $$. So I'd like to try a few things that mght have a chance of working before doing that.

Here's the only schematic I can find that shows the transisitor and resistor on the board, but no info as to what the parts are. Also, can't find what is connected to the base. I can swap out the parts from the component side of the board OK, but can't trace the leads or it would likely damage something else on the baord -- due to the condition of the board. I just need the car to pass smog so I can continue restoring the car, but dont want to put a lot of money into anything until I'm sure the car is worth it.

Thanks in advance!

Bob

Thanks.

Bob

Was having trouble focusing, but these are somewhat clear...

... connects to this component unfamiliar to me. Anyone recognize it? It is labeled CM104. Can't get a clear view for a photo. Rough sketch....

Most connections on this part of the board are underneath parts I can't get to. No markings on it that I can see. There are 7 of these on the board, all packed close together under a metal piece which is not practical to remove.

Anyway.... my problem is the Check Engine light does not illuminate. The bulb and all circuits external to the ECU board are fine. The board is also good between the 12VDC into the board from the bulb and ground. I suspect the trouble is the transistor or associated capacitor, but the board has been worked on before and the markings on these parts are no longer readable.

So, without a schematic, I wonder if someone more familiar with this type of circuit could guess at a possible replacement for the transistor and capacitor.

I know this is not the "proper" way to do it, but the alternative is buying a new ECU - several hundred $$. So I'd like to try a few things that mght have a chance of working before doing that.

Here's the only schematic I can find that shows the transisitor and resistor on the board, but no info as to what the parts are. Also, can't find what is connected to the base. I can swap out the parts from the component side of the board OK, but can't trace the leads or it would likely damage something else on the baord -- due to the condition of the board. I just need the car to pass smog so I can continue restoring the car, but dont want to put a lot of money into anything until I'm sure the car is worth it.

Thanks in advance!

Bob

Thanks.

Bob

It looks like a resistor ladder.

Regards, Rob

it? It is labeled CM104. Can't get a clear view for a photo. Rough sketch....

can't get to. No markings on it that I can see. There are 7 of these on the board, all packed close together under a metal piece which is not practical to remove.

The bulb and all circuits external to the ECU board are fine. The board is also good between the 12VDC into the board from the bulb and ground. I suspect the trouble is the transistor or associated capacitor, but the board has been worked on before and the markings on these parts are no longer readable.

type of circuit could guess at a possible replacement for the transistor and capacitor.

buying a new ECU - several hundred $$. So I'd like to try a few things that mght have a chance of working before doing that.

resistor on the board, but no info as to what the parts are. Also, can't find what is connected to the base. I can swap out the parts from the component side of the board OK, but can't trace the leads or it would likely damage something else on the baord -- due to the condition of the board. I just need the car to pass smog so I can continue restoring the car, but dont want to put a lot of money into anything until I'm sure the car is worth it.

send a few $$ for a copy. I need to troubleshoot the check engine light circuit and have traced it to the ECU circuit board.

entering/leaving the board, one cap per signal to a common ground pin. It may however be the cause of your problem though, as I see from your pics that someone has replaced the electrolytic capacitors which are renowned for leaking. They can cause much grief initially and again some years later. The electrolyte from the leaking caps can eat away the copper tracks if it hasn't been cleaned effectively. From the pics you have uploaded it looks like TR3 in the gif image wyu is the CEL lamp driver. The large flat pad should lead to a small value resistor, possibly 3.3 ohms (colour bands orange orange gold). Check for continuity between ECU terminal 64 and what should be the closest end of that low ohm resistor. If you have continuity then it might be a real component failure not just a track eaten away. I will upload a pic of an ecu I have here but the component designation numbers are different. If you can upload a downwards looking pic that covers both sides of the thick film hybrid IC101 (E518 on back) that would help.

no success. It's all just reverse engineering.

Here are some shots of a Galant ECU and my "Montero" which had been previously repaired - badly. Apologies in advance for the screwed up order.

The CEL control in both ECUs is functionally identical, only the names have been changed.

The close-ups of the CM106 location show the tracks corroded away by the remaining electrolyte.

===

Thanks, Mark! That's a great help. Here are some new photos

This photo index might help you find the ones you want to see. All except #10 are in the 800K range.

1 2 3 4 5 6 7 8 9 10 TR3 Closeup Bob

it? It is labeled CM104. Can't get a clear view for a photo. Rough sketch....

can't get to. No markings on it that I can see. There are 7 of these on the board, all packed close together under a metal piece which is not practical to remove.

The bulb and all circuits external to the ECU board are fine. The board is also good between the 12VDC into the board from the bulb and ground. I suspect the trouble is the transistor or associated capacitor, but the board has been worked on before and the markings on these parts are no longer readable.

type of circuit could guess at a possible replacement for the transistor and capacitor.

buying a new ECU - several hundred $$. So I'd like to try a few things that mght have a chance of working before doing that.

resistor on the board, but no info as to what the parts are. Also, can't find what is connected to the base. I can swap out the parts from the component side of the board OK, but can't trace the leads or it would likely damage something else on the baord -- due to the condition of the board. I just need the car to pass smog so I can continue restoring the car, but dont want to put a lot of money into anything until I'm sure the car is worth it.

send a few $$ for a copy. I need to troubleshoot the check engine light circuit and have traced it to the ECU circuit board.

entering/leaving the board, one cap per signal to a common ground pin. It may however be the cause of your problem though, as I see from your pics that someone has replaced the electrolytic capacitors which are renowned for leaking. They can cause much grief initially and again some years later. The electrolyte from the leaking caps can eat away the copper tracks if it hasn't been cleaned effectively. From the pics you have uploaded it looks like TR3 in the gif image wyu is the CEL lamp driver. The large flat pad should lead to a small value resistor, possibly 3.3 ohms (colour bands orange orange gold). Check for continuity between ECU terminal 64 and what should be the closest end of that low ohm resistor. If you have continuity then it might be a real component failure not just a track eaten away. I will upload a pic of an ecu I have here but the component designation numbers are different. If you can upload a downwards looking pic that covers both sides of the thick film hybrid IC101 (E518 on back) that would help.

no success. It's all just reverse engineering.

Here are some shots of a Galant ECU and my "Montero" which had been previously repaired - badly. Apologies in advance for the screwed up order.

The CEL control in both ECUs is functionally identical, only the names have been changed.

The close-ups of the CM106 location show the tracks corroded away by the remaining electrolyte.

===

Thanks, Mark! That's a great help. Here are some new photos

This photo index might help you find the ones you want to see. All except #10 are in the 800K range.

1 2 3 4 5 6 7 8 9 10 TR3 Closeup Bob

===

PS -- Checking - no continuity between pin 64 and any of TR3 contacts. Also, I checked 64 to R104 and all other transistors & resistors I could find in that part of the board and no continuity with any of them.

The trace from CM104 goes under CM105 which I can see is badly corroded. Looks like I will need to remove the power transistor heat sink, clean that up and just go one step at a time.

Stay tuned! =O)

a few $$ for a copy. I need to troubleshoot the check engine light circuit and have traced it to the ECU circuit board.

Bob, are you sure R104 is the target resistor? From your latest pics it appears to be 2200 ohms - which to me is too high for the CEL activation circuit. The value should be well below 1000 ohms. If you are absolutely sure it's R104 then proceed to remove the heat sink as follows.

There is a small circular raised section in the heat sink for each transistor plus a small amount of heat sink transfer compound . They form a mechanical and thermal bond to the mounting surface of the transistors. Once you release the clamping screws and plate, gentle prying should free the transistors from the heat sink. Next is the tricky part. This is what I do to remove the heat sink: I start with a

1/16 drill in the center of the Philips recess and then increase the drill size by 1/64 steps being very careful not to go too deep. Eventually you should achieve release using a 9/64 drill. If you go too deep there's a risk of damaging the thread in the aluminum heat sink. Later you will need a high wattage sodering iron to remove the remaining portion of the screw head ( I use a HarborFreight Tools 180W iron.

Again, the critical thing is to take your time. Regards - Mark.

===

Hi Bob. Thanks for the info about removing the heat sink, etc. That will come in handy when I get back to it later.

I gave up trying to find which resistor and transistor were in the circuit. A little cleaning got the Check Engine Light to work, so it passed the smog test which was the first step. Now I can spend some time trying to find a good used ECU. Then I'll finishing troubleshooting it and post any results here.

Like the song says, you have to know when to hold 'em and when to fold 'em, know when to walk away and know when to run!! LOL!!

Bob

a few $$ for a copy. I need to troubleshoot the check engine light circuit and have traced it to the ECU circuit board.

Bob, are you sure R104 is the target resistor? From your latest pics it appears to be 2200 ohms - which to me is too high for the CEL activation circuit. The value should be well below 1000 ohms. If you are absolutely sure it's R104 then proceed to remove the heat sink as follows.

There is a small circular raised section in the heat sink for each transistor plus a small amount of heat sink transfer compound . They form a mechanical and thermal bond to the mounting surface of the transistors. Once you release the clamping screws and plate, gentle prying should free the transistors from the heat sink. Next is the tricky part. This is what I do to remove the heat sink: I start with a

1/16 drill in the center of the Philips recess and then increase the drill size by 1/64 steps being very careful not to go too deep. Eventually you should achieve release using a 9/64 drill. If you go too deep there's a risk of damaging the thread in the aluminum heat sink. Later you will need a high wattage sodering iron to remove the remaining portion of the screw head ( I use a HarborFreight Tools 180W iron.

Again, the critical thing is to take your time. Regards - Mark.

===

Hi MARK. Thanks for the info about removing the heat sink, etc. That will come in handy when I get back to it later.

I gave up trying to find which resistor and transistor were in the circuit. A little cleaning got the Check Engine Light to work, so it passed the smog test which was the first step. Now I can spend some time trying to find a good used ECU. Then I'll finishing troubleshooting it and post any results here.

Like the song says, you have to know when to hold 'em and when to fold 'em, know when to walk away and know when to run!! LOL!!

Bob

I meant..... Hi Mark (I'm Bob...duheeee)... And thanks again.