CEL, GMPP harness for LS3 - Lateral-g Forums

DT69Cam · #1 07-28-2016, 12:21 PM

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** · #2 07-29-2016, 04:32 AM

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** · #3 07-29-2016, 06:26 AM

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 · #4 07-29-2016, 12:04 PM

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 · #5 07-29-2016, 12:19 PM

Quote:

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 · #6 07-29-2016, 02:50 PM

Quote:

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)