Check engine light stays lit but can't connect to ECU..

[90 GSX]

I just put an ECU rebuilt in 2003 (looked immaculate inside) in my 91 talon. With the bad ecu, the thing started and idled fine. With this new ecu, it just keeps crankin. Also, the check engine is supposed to come on briefly and then turn off but it just stays lit. Another weird thing, one of the solenoids (fuel pressure methinks) in the corner of the engine bay by the fuel pressure regulator kept clicking on and off and subsequently I could hear the injectors clicking away but the car didnt want to start. This clicking happened with the key turned to the on position and a few seconds after the key was turned off and removed. I also think I noticed the check engine light get a little dim when the solenoid start going but that could be natural.

The car is federal but I put in a CA ecu, does that make a difference? I thought the only difference was the egr solenoid and temp sensor. Could the new ECU be bad? What else could cause that?

 

[i1nk83]

sounds like you got a bad ecu return it and get a new one

 

[steve]

Could the new ECU be bad?

Sounds like it. The clicking and rest sound like the ECU has gone off and started executing random code. Is the new one an EPROM, maybe you have a bad chip?

Steve

 

[PieTSI]

Reseat all of the connectors on the ECU before returning it. This can be a common problem.

 

[BoostedTalonTS]

Once connected, have you tried to take a multimeter to the OBD1 diagnostic port pins # 1 & 12? What does it say if you meter voltage?

 

[90 GSX]

Reseated connectors and it worked. Thanks fellas.

 

[Mike000]

Once connected, have you tried to take a multimeter to the OBD1 diagnostic port pins # 1 & 12? What does it say if you meter voltage?

What are the values suppose to be?

 

[steve]

Pin 12 is ground and pin 1 will switch between 0 and 12v (battery voltage) in a 50% duty cycle if the ECU is up and running and has no codes. If there are codes the ECU will put out long 12v pulses for the 10's digits and short ones for the units.
If pin 1 is 12v all the time the ECU is dead(at least for now)

Steve

 

[BoostedTalonTS]

What are the values suppose to be?

If everything is AOK, then it should read: (with the key in the Ignition position)

Voltage, no voltage, voltage, no voltage, voltage, no voltage, ect, ect... (Indicating no error codes stores in the ECU, and the ECU checks out OK)

If there is a problem, then it will have a pattern to the "voltage pulses" (a cheap-o Radio Trash analog multimeter works great for the test @~$10), just count the sweeps of the needle, noting if the pulses are long or short... The longer pulses indicate the first digit (?x)or the trouble codes stored in the ECU, while the quick pulses indicate the second digit of the stored code (x?)... ie: Long, Long, Short, Short, Short, Short pulses = Error code 24 (Vehicle Speed Sensor fault)

The ECU will "display" all of codes that are currently stored then repeat them until the Ignition is turned off.

If you have no pulses at all, then the ECU isn't working correctly.

Another good thing to do is pull the 40Amp "Battery" fuse in the front Passenger's Side fuse box under the hood, BEFORE you plug in your ECU then replace it after you install the ECU.

Here is another explanation & a listing of the codes:


http://www.vfaq.com/mods/wayback/BradBauer/electrical/code.html

Most of the 1G dataloggers that are currently available also incorperate this code retrieval function into the logger itself, making it that much more of a good thing to have around for your DSM. If you don't already have one, I would invest in one pronto! -In fact, If you want one, I have an old one that I don't use anymore... PM me for more info if you are interested in it.