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Discussion Starter #1
I recently bought a 2011 2500HD Duramax with PPEI Autocal & has been deleted. Love the truck but I'm having issues with the glow plugs. They are only getting 1 volt or under when key is turned on. I've replaced all the glow plugs with ones from Diesel RX, replaced the glow plug controller. (programmed the injector rates to the new module). I can't get the truck to start when its below 30 degrees. I've checked all the temp sensors & they are ok.
When the key is turned on the voltage will go to 3 volts briefly then down to 1 volt or under for several seconds. I hooked up a glow plug to the harness & it was barely getting warm at this voltage.

Any ideas?
 

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jokerfabworx.com
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Let's bump this up. My 2011 is doing the exact same thing.
-About 0.95 volts at the plugs (both on the stud and the harness' lug) when the plugs are 'on', triggered with a Tech II or by the ignition.
-Resistance on all plugs is good when checked with a mulitmeter and in the Tech II.
-No DTCs or CEL.
-Replaced GPM and flashed injector info. No change.

The plugs are pulse width modulated after the first two (2) seconds of operation. Could the ECM cause this?

Educated answers only please.
 

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Discussion Starter #3
JOKER, I replied to your pm, but am going to post here also for others to see.

My truck had been tuned by PPEI before I bought it. The first time I contacted them about the glow plug issue, they said they would not have been affected by their tuning. I had access to Alldata at the time so I got the schematic for the glow plug harness, inspected it, ohm'd each wire and load tested each wire. I had new A/C Delco glow plugs and a new Glow plug controller that had been programmed to the truck. That left only the PCM to be the problem. I contacted PPEI again explaining all that I had replaced & tested. They emailed me new files to upload to the autocal. I reprogrammed the truck with a new tune and the glow plugs seem to be working. Since then the coldest we have had is in the 20's, I'm waiting for a colder morning before I'm going to be completely convinced it's fixed though.
 

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jokerfabworx.com
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Right on, Ken. I got new tunes from my tuner as well, but the same issue is there.

I flashed the ECM to stock, flashed it with old H&S tunes, flashed it back to stock, and then again with EFI Live tune. Still under 1 volt with all of those flashes.

How much voltage are your plugs seeing now?
 

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Discussion Starter #5
I haven't checked voltage since the retune. The first morning below freezing (coming soon), I'll leave it outside overnight & check things out. I'll be sure to let you know.
 

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This information pertains to my 2008 LMM. I'm assuming yours is much the same.



Glow Plug System Description

In the diesel engine, air alone is compressed in the cylinder. Then, after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs, due to the heat of compression. Eight glow plugs are used as an aid to starting.

Control of the instant start system (ISS) glow plugs is accomplished by a glow control module unit and 4.7 volt glow plugs, requiring 2 seconds to heat up to 1,000°C (1,832°F). The temperature and the power consumption is controlled between the engine control module (ECM) and the controller within a wide range to suit the engine's pre-heating requirements. Each glow plug is energized individually. This capability yields more optimum heat times for the glow plugs, thus pre-glow times can be kept to a minimum for short wait to crank times and maximum glow plug durability. A DTC will set if there is a glow plug system fault.

A normal functioning system operates as follows:



  • Turn the ignition ON with the engine OFF, and at room temperature.
  • The glow plugs turn ON and heat up in 2 seconds and then are pulse-width modulated (PWM) for another 2 seconds.
  • The glow plug wait lamp is ON for 1 second during cold start.
  • The glow plug wait lamp may not illuminate during a warm engine start.
  • If the engine is cranked during or after the above sequence, the glow plugs may cycle ON and OFF after the ignition switch is returned from the start position, whether the engine starts or not. The engine does not have to be running to terminate the glow plug cycling.
The glow plug initial ON time will vary based on the system voltage and temperature. Lower temperatures cause longer ON times.

The ECM provides glow plug operation after starting a cold engine. This post-start operation is initiated when the ignition switch is returned to Run, from the Start position. This function helps clean up excessive white smoke and/or poor idle quality after starting.

Glow Plugs

The glow plugs are 4.7 volt heaters in each of the cylinders that turn ON, then pulse-width modulated when the ignition switch is turned to the RUN position prior to starting the engine. They remain pulsing a short time after starting, then they are turned OFF.

A Wait to Start lamp on the instrument panel provides information on engine starting conditions. The Wait to Start lamp will not illuminate during post-start glow plug operation.

Glow Plug/Controller

The glow plug controller is a solid state device which operates the glow plugs. The glow plug controller is connected to the following circuits:



  • The fuel heater ignition 1 voltage circuit
  • The battery voltage circuit
  • The CAN communication circuit located between the engine control module (ECM) and the glow plug controller
  • The engine ground circuit
  • The glow plug supply voltage circuits located between the glow plug controller and the glow plugs.
The glow plug diagnostic circuits are directly monitored individually by using a separate transistor to control current to each glow plug. Individual diagnosis is thus possible for every glow plug.
 

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Glow Plug

This information pertains to my 2008 LMM. I'm assuming yours is much the same.



Glow Plug System Description

In the diesel engine, air alone is compressed in the cylinder. Then, after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs, due to the heat of compression. Eight glow plugs are used as an aid to starting.

Control of the instant start system (ISS) glow plugs is accomplished by a glow control module unit and 4.7 volt glow plugs, requiring 2 seconds to heat up to 1,000°C (1,832°F). The temperature and the power consumption is controlled between the engine control module (ECM) and the controller within a wide range to suit the engine's pre-heating requirements. Each glow plug is energized individually. This capability yields more optimum heat times for the glow plugs, thus pre-glow times can be kept to a minimum for short wait to crank times and maximum glow plug durability. A DTC will set if there is a glow plug system fault.

A normal functioning system operates as follows:



  • Turn the ignition ON with the engine OFF, and at room temperature.
  • The glow plugs turn ON and heat up in 2 seconds and then are pulse-width modulated (PWM) for another 2 seconds.
  • The glow plug wait lamp is ON for 1 second during cold start.
  • The glow plug wait lamp may not illuminate during a warm engine start.
  • If the engine is cranked during or after the above sequence, the glow plugs may cycle ON and OFF after the ignition switch is returned from the start position, whether the engine starts or not. The engine does not have to be running to terminate the glow plug cycling.
The glow plug initial ON time will vary based on the system voltage and temperature. Lower temperatures cause longer ON times.

The ECM provides glow plug operation after starting a cold engine. This post-start operation is initiated when the ignition switch is returned to Run, from the Start position. This function helps clean up excessive white smoke and/or poor idle quality after starting.

Glow Plugs

The glow plugs are 4.7 volt heaters in each of the cylinders that turn ON, then pulse-width modulated when the ignition switch is turned to the RUN position prior to starting the engine. They remain pulsing a short time after starting, then they are turned OFF.

A Wait to Start lamp on the instrument panel provides information on engine starting conditions. The Wait to Start lamp will not illuminate during post-start glow plug operation.

Glow Plug/Controller

The glow plug controller is a solid state device which operates the glow plugs. The glow plug controller is connected to the following circuits:



  • The fuel heater ignition 1 voltage circuit
  • The battery voltage circuit
  • The CAN communication circuit located between the engine control module (ECM) and the glow plug controller
  • The engine ground circuit
  • The glow plug supply voltage circuits located between the glow plug controller and the glow plugs.
The glow plug diagnostic circuits are directly monitored individually by using a separate transistor to control current to each glow plug. Individual diagnosis is thus possible for every glow plug.
Any idea on what ambient temperature the glow plugs become inactive?
 

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Discussion Starter #10
Joker, I left my truck outside last night as it was going to be in the 20's this morning. I got 4.9V at the glow plug when I turned the key on. . The voltage stayed at 4.9 for several seconds after the light went out, then dropped to zero. I tried it a 2nd time with the same results.
 

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Discussion Starter #12
Mine was a programming issue. Since they sent me new files & I reprogrammed the truck with them, the glow plugs are working.
Also check the harness by the A/C line. I guess there can be a rub through issue on some trucks.
 

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jokerfabworx.com
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Joker, I left my truck outside last night as it was going to be in the 20's this morning. I got 4.9V at the glow plug when I turned the key on. . The voltage stayed at 4.9 for several seconds after the light went out, then dropped to zero. I tried it a 2nd time with the same results.
Glad yours is fixed man. Didn't PPEI tell you that their tuning shouldn't affect the GP operation? That is what Motor Ops told me.

Mine was a programming issue. Since they sent me new files & I reprogrammed the truck with them, the glow plugs are working.
Also check the harness by the A/C line. I guess there can be a rub through issue on some trucks.
I'll be pulling the harness out when I get a chance.

I appreciate the feedback. :thumb
 

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Discussion Starter #14
The first time I talked with PPEI, they said the tuning has nothing to do with the glow plugs. That's when I replaced the module, glow plugs (twice), and load tested each wire in the harness. I contacted them again, explaining everything I had done & had it narrowed down to either the PCM or the tuning. They sent me new files & thankfully everything is fine now. Their support is superb in my book. My truck was tuned before I bought it & I expected the too bad so sad treatment.
 

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jokerfabworx.com
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Has this issue popped up for anyone else? I poked around my truck a little to check grounds, but not much more than that. I don't know if Ken's has been behaving or not.

Flashing back to stock doesn't change anything. I even broke down and took it to two different dealers. They both say that the GP system is functioning properly (according to their diagnostic tools).

A crude GP override might be in the works...
 

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Discussion Starter #16
Joker, I went through all the trouble of making a harness and installing a button for the glow plugs. The problem I ran into was finding something to reduce the voltage down to 5 volts that could handle the amperage needed. The truck will not start if you mess with the GP controller, found that out the hard way.
My glow plugs are no longer working like they're supposed to. Below 30 degrees it's a bear to start, but if I plug it in for as little as an hour it will start right up. I'm not going to dig into it anymore, I have a heated garage to keep it in. Frustrating for sure.
 
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