I did an engine swap. The new Toyota engine has its own ecu. I am trying to connect to the CEL wire to access trouble codes. I have tried a small gauge light hooked up to it to see if it would flash, but nothing happens. How low of a voltage is this wire's output that it won't make a small bulb flash? The engine is a 94 Lexus GS300
Need to connect to check engine light wire from ecu... Toyota
- Thread starter daves66nova
- Start date
How are you connecting the light? Most all ECU outputs are "current sinking" so the light needs to be connected between +12V and the output.
I'm under the assumption that the wire puts out some voltage, so I hooked up a small oil pressure gauge style light bulb and grounded it, to see if it would flash the codes. "Current sinking"? Never heard of that.
Don't know if this is how yours is built but we put a jeep 4.0 in my old bosses 89 wrangler. The engine and related wires, computer etc came from a 2000 grand Cherokee. The check engine light in that jeep cherokee was turned on like blue tooth.
No wires but a radio signal instead
No wires but a radio signal instead
Yes, "current sinking". Did you ever notice that practically everything an ECU switches on and off is done by having the ECU in the ground side of the circuit? Fuel injectors, solenoids, relays...and the check engine light.
Here's a couple of examples of how the check engine light is wired between +12V and the ECU.
One is from a Toyota, one is from a GM. Ford does the same thing. I'm fairly confident that they are ALL wired that way until you get into newer vehicles with a databus between the instrument cluster and the ECU.
Attachments
So , I would need to add 12v to the bulb and use the ecu wire to ground the bulb?
Yes. The 12V should be switched, not constant (assuming you are going to wire this permanently).
The light did turn on, supplying 12v to it, but, even after jumping the diagnostic wire, the bulb does not blink at all, it just stays on. Do you know why? Thanks
Just remembered, battery has been disconnected about 24 hours or so. Code erased? Anyway, I got the engine turned on, let's see if it throws a code now........
Ran it, disconnected a sensor or 2 while running, turned off, checked for codes, nothing. Even swapped out ecu with another one, did the same procedure, still nothing......
Does the light turn off when the engine is running or does it stay on? If it's working correctly, it should turn off when the engine runs, unless there's a code.
May need a wiring diagram to troubleshoot further.
May need a wiring diagram to troubleshoot further.
When it's hooked up, it stays on when the ignition is on, once i cut ignition, it turns off.
????????
I found a wiring diagram for a 1995 Lexus GS300.
See if your wiring matches what's on page 74 and 75 of that PDF. It shows the check engine light connected to 12V and the other side of the light (the ground side) on a black/yellow wire to pin 6, connector A of the ECU.
See if your wiring matches what's on page 74 and 75 of that PDF. It shows the check engine light connected to 12V and the other side of the light (the ground side) on a black/yellow wire to pin 6, connector A of the ECU.
Sorry for the late reply. My connector looks like D 1 Black on page 74.
I think i found the problem. I was told to check the ecu. Sure enough, the ecu had many burnt capacitors. We fixed it, now we just gotta get an ignitor. supposedly those also go out. We tried checking for spark, no spark.
FWIW, that is what Toyota calls the Diagnostic Connector or DLC1. It's typically under the hood attached to the engine via some kind of bracket.
Not surprised that you found leaking capacitors in the ECU:
All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor) - ClubLexus - Lexus Forum Discussion
LS - 1st and 2nd Gen (1990-2000) - All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor) - 430230 *photo courtesy of distinguished Japanese ECU engineer Yamae 430231 IMPORTANT: The capacitors may look perfectly fine and yet be bad, they look great at first, then deteriorate and cause damage...
www.clublexus.com
Yeah, that's where i found out about the ecu. Still no spark, and i tried different ignitors. What else can i check?FWIW, that is what Toyota calls the Diagnostic Connector or DLC1. It's typically under the hood attached to the engine via some kind of bracket.
Not surprised that you found leaking capacitors in the ECU:
All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor) - ClubLexus - Lexus Forum Discussion
LS - 1st and 2nd Gen (1990-2000) - All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor) - 430230 *photo courtesy of distinguished Japanese ECU engineer Yamae 430231 IMPORTANT: The capacitors may look perfectly fine and yet be bad, they look great at first, then deteriorate and cause damage...www.clublexus.com
