Check engine light and diagnostics

TruckA · Post by **TruckA** » Wed Apr 12, 2006 7:48 pm

Anyone have any luck in setting up the check engine light? I'm not sure if I have mine wired up quite right and I'd like to know how anyone else wired up a light. I bought a separate indicator light that I would like to use. Also, as far as obtaining diagnostic codes, anyone have a good setup? I think I may finally be able to take my truck out for a drive this weekend, but I definately want to run a diagnostic check and make sure my check engine light is working before leaving the driveway.

Thanks!

peregrine · Post by **peregrine** » Wed Apr 12, 2006 11:46 pm

i wired in the stock doagnostic port. its easy. two wires and a ground. i dont have a check engine light but i have dsmlink which allows me to check for codes as well as tune it. if you need the diagram for the diagnostic port let me know.

Mike · Post by **Mike** » Thu Apr 13, 2006 2:53 am

Well, if it's working it should come on and go off momentarily when you start the engine. Is that what you wanted to know?

TruckA · Post by **TruckA** » Thu Apr 13, 2006 6:11 am

Right now its not coming on when I start the car. I have a cord that came with the donor car for the dsmlink, but I do not have the harness connector for the diagnostic port. I've got another spare harness, so I'm going to search for an identical connector to the stock diagnostic port and wire it as peregrine describes. So if you do have a diagram peregrine, it would help, but I probably can figure it out if not. I'd still like to have the check engine light, so I'll mess with that just a little more.

peregrine · Post by **peregrine** » Thu Apr 13, 2006 12:12 pm

DLC pin 1 to ECU pin 1.
DLC pin 10 to ECU pin 2.
DLC pin 12 to ground.
Pin 1 on the DLC has a Yellow wire.
Pin 10 on the DLC has a White wire.
Pin 12 on the DLC has a Black wire.

tjc · Post by **tjc** » Thu Apr 13, 2006 5:34 pm

I also wired the diagnostic port to the ECU as above. I log and read codes with MMCd and a palm IIIx, but before that I just used an analog voltometer (black to pin 10 or 12 and red to pin 1) and count the long and short sweeps to get codes.
I did not wire a check engine light.

Tim

I also looked for a similar plug to the DLC on a spare harness, they are all different. I got mine at a junk yard off a NT but your right, any male plug will work.

TruckA · Post by **TruckA** » Thu Apr 13, 2006 6:43 pm

Thanks for the info peregrine and tjc, I will attempt to wire it up this weekend. Are you guys not concerned with putting in the check engine light? I guess I'm concerned with something going wrong when I'm driving and not noticing it until its too late.

Thanks again!

peregrine · Post by **peregrine** » Thu Apr 13, 2006 6:50 pm

TruckA wrote:Thanks for the info peregrine and tjc, I will attempt to wire it up this weekend. Are you guys not concerned with putting in the check engine light? I guess I'm concerned with something going wrong when I'm driving and not noticing it until its too late.

Thanks again!

honestly, if you put the time and effort into doing everything right you should have no worries. you should by all means have gauges for everything. oil pressure, voltage, coolant etc. if you can keep an eye on these things a check engine light becomes redundant. remember, when wiring in the port to solder it in. if you use vampire clips or anything else it will cause resistance and not work. JFYI

Post by **DJpowerHaus** » Thu Apr 13, 2006 9:57 pm

If I would have taken the time to put a check engine light in I would have had to find a way to cover it up becuase that thing was always on.

But on a side note.. maybe its grounded by the ECU to turn the light on. This would mean that you run a positive to the (+) of the light and the ECU CEL wire acts as (-) to complete the circuit.

I know that's how most aftermarket ECU's work.

TruckA · Post by **TruckA** » Fri Apr 14, 2006 5:22 pm

You were right DJPowerhaus, connect one side of the light to a positive, and the negative to ECU CEL pin, and it works. It sucks because it it is on now, but that's no biggie. Time to run the diagnostics. It finally runs well, but has idle surge, but the annoying high pitched squeal I've been experiencing has disappeared. I actually may be driving this weekend, woo hoo, except I have a 500 mile break in for the clutch.

TruckA · Post by **TruckA** » Sat Apr 15, 2006 11:47 am

Update,

The only code showing is for the Fuel Pump, code 42. So I'll have to figure out whatever signal usually satifies the computer from the fuel pump system to turn the light off since I'm using an external walbro pump.