CEL, GMPP harness for LS3

[DT69Cam]

Does anyone know if the "Check Engine Light" on the GMPP LS3 harness is triggered by a negative source ?? My new gauges CEL needs a positive trigger for the light to turn on. I know I need a relay to convert from neg to positive. I just wanted to confirm the negative source for the CEL. Thx.

[130fe]

What gauges are you running? I am currently running the VHX gauges and just have the CEL wire from the GMPP bulkhead wired directly into their control box. I used the have an LT1 (before the LS3) using an another companies EFI harness and it did provide the negative side of the circuit from the PCM side. I just had to hook the other side of the LED to an IGN source.

[TomM]

Typically you supply the CEL with a keyed/fused +12V circuit. The ECM switches a negative signal to the CEL when a DTC is set. Easy way to check if you have HP Tuners is to toggle the CEL with the software.


T,

[DT69Cam]

Thanks guys for the reply. I'm using New Vintage Gauges 69 series 3 in 1. The gauges call for a positive trigger (12V) on the warning lights. I know the parking brake is triggered via a ground. I will be using a relay to convert neg to positive for the brake light in the gauge. I also think the CEL is triggered via a ground, so in order for the CEL to light up in the gauge I have to convert it to positive, (another relay).

[dhutton]

Originally Posted by DT69Cam

Thanks guys for the reply. I'm using New Vintage Gauges 69 series 3 in 1. The gauges call for a positive trigger (12V) on the warning lights. I know the parking brake is triggered via a ground. I will be using a relay to convert neg to positive for the brake light in the gauge. I also think the CEL is triggered via a ground, so in order for the CEL to light up in the gauge I have to convert it to positive, (another relay).

I am not sure that the CEL signal can drive a relay. What is the coil resistance of the relay you are using?

Don

[DT69Cam]

Originally Posted by dhutton

I am not sure that the CEL signal can drive a relay. What is the coil resistance of the relay you are using?

Don

You know Don I am not exactly sure. Typical 30a Bosch relay. The relay is just converting from negative to positive trigger (reverse polarity)

[dhutton]

Originally Posted by DT69Cam

You know Don I am not exactly sure. Typical 30a Bosch relay. The relay is just converting from negative to positive trigger (reverse polarity)

I guess you can try and see if it works. 30A is a bit of overkill for this application.

Something like this is all you need:

http://www.ebay.com/itm/2pcs-Blue-41...QAAOSwT6pV4XRo

Don

[DT69Cam]

Originally Posted by dhutton

I guess you can try and see if it works. 30A is a bit of overkill for this application.

Something like this is all you need:

http://www.ebay.com/itm/2pcs-Blue-41...QAAOSwT6pV4XRo

Don

I agree the 30a is overkill. That small signal relay looks pretty good. Hmmm.

[dhutton]

Originally Posted by DT69Cam

I agree the 30a is overkill. That small signal relay looks pretty good. Hmmm.

You could also use a simple single transistor inverter. Not sure if you are comfortable with wiring something like that. I have the same gauges and will go that route when I finally get to wiring them up.

Don

[dhutton]

This Bosch 12V 30A relay has a coil current of 160 mA which is a lot more than an LED.

http://www.texasindustrialelectric.c...0332209150.asp

I will dig around and see if I can find the CEL current capability.

Don