I found this site today and decided to sign up. I need some direction. I have a 2000 F250 SD 7.3 California Truck. The truck is having hard starts and I decided to change out glow plugs and install the LED Light Mod. The glow plugs were changed without issue but I have a question or two regarding the LED light. The LED installation went well but I seem to not have power thru the relay. I have 12v to one side of the relay but when I turn the key to KOEO there is no voltage to the other side of the relay. The relay doesn't click when power is applied. The two small wires on each side of the relay show power. I would think the relay is bad. This truck has the glow plug control module also. Where do I hook up the LED power wire, to the relay right? Could both the relay and control module be bad? If so, wouldn't an SES light trigger? Thanks in advance for any input.

 

If you have a Kalifornia truck, you don't have a glow plug relay. You have a GPCM which is a different animal.

You have this with CA emissions.



The relay you do have is the air intake heater.

 

Hi Chris....Thanks for the diagram and reply. Do you happen to know where I would hook up the LED light on this system?

 

Here's the picture I meant to post. It has a little more detail.



I've never hooked one up on a GPCM. You could either pull the hot lead for your light from any of the wires heading to a glow plug, or since those wires can trip a code if the readings are off, you can check for which wire is the ground signal.

I'm assuming the GPCM is activated by a ground signal from the PCM since it looks like they have battery voltage wired directly to the connectors.

I'd use a multi-meter and check the pk/o (should be pink wire with orange tracer) from PCM pin 101 to see if it gives a ground signal when the key is first turned on. If that doesn't work, check the w/lg (white / light green) wire from PCM pin 8. The Vref should be a 5 volt reference signal and the battery voltage should be your 12v from the battery.

If you can find the ground signal, hook up the LED to a fused 12v power source and then hook the other lead to the wire you find that sends the ground signal.

 

I always wondered how to hook up a GP mod light on my X. Let us know how u did it if you get it to work. Would like to do it on the X.

 

Thanks for the additional info. I'll take a look this coming weekend.

Doc

 

subscribing...buddys' ride has the module, and wants the gpr-led too

 

I was intrigued, so I'm jumping in. Pin 41 on the 42-pin connector is common from the PCM, and pin 13 is the GP control signal. I don't advocate tapping into a control signal from the PCM (impedance change may bugger up the circuit). No matter what you do, you're tapping into a wire to get your signal - this is opposed to the easy task of putting a pair of connectors on a GPR.

The best I can suggest is to tap into one glowplug wire for your hot signal (pardon the pun) to the LED, and ground the other end of the LED in the cab. This will tell you when that single glowplug is active, and the wiring is setup up so that they are all on at the same time.

Tying into a GP wire is a little tricky - those cheap crimp splices would introduce corrosion and eventual failure with this current and environment. This is a strip, solder, and seal task.

 

You don't think tying into a hot wire will mess with it more? I really don't know, but I'm guessing the GPCM measures resistance to the plug wire the same way we do with a meter, and tapping in a wire might throw that off. If the control wire is just a ground signal, I would have guessed that to be safer.

This comes with the qualification that I actually have no friggin idea what the correct answer is. Tapping into a hot wire would be the easiest method.

I guess if you go that route first and get a CEL, then you can always switch to plan B.

 

I guess since nobody else has asked, I will. Given the fact that a malfunction in the glow plug system on a truck with a control module will set a DTC and MIL, why bother with an indicator light?

 

I didnt think a truck or X with a control module set a DTC if it had a malfunction.

 

Yes it does. That's the whole thought behind the CA emissions. If it might cause just a tad more smoke from a faulty glow plug, a CEL should be tripped so it can be fixed immediately.

The glow plug codes are OBDII codes, so the auto parts stores or cheap readers (since CA won't allow a parts store to read codes for free) can read them.

 

The impedance (electrical resistance) of an LED is so much higher than a GP, putting it in parallel with a GP will not have any effect that the GPCM could measure. The GPCM input is a different matter. It has much higher resistance than a GP, and I can't say what an LED in parallel to the control circuit will do, except bring the whole circuit resistance down in a measurable way. Will it be enough to trip something up? I have no idea... but it still involves stripping, soldering, and sealing. I'd rather go through that procedure just one time.

The GPCM does have diagnostics, so the LED mod could very well be superfluous.

 

... and quite a while back, in another of the longer GPR LED status indicator threads, someone tossed out the possibility of using a 10-segment LED bar graph indicator and tapping into each of the 8 GP power wires so that you could see if any individual GP lost its input from the GPCM, and even know which one it is!

 

That takes **** to a whole new dimension. Work out the pun, guys.