Help with 03 duramax CA emissions glow plug/controller issue ☆ problem solved☆

[Dirtymaxx88]

☆edit: PROBLEM SOLVED, READ LAST POST☆

Hey yall. New to the forums but could use some help with a duramax glow plug issue.
I dont see a help forum page, not sure where this goes..

2003 GMC sierra duramax
6.6 auto
California Emissions

Working on a customer vehicle. Its having a glow plug issue with a P0380 code. I've read though hours of googling p0380 and duramax gp issues.

1.) I cant seem to get the plugs to cycle on or 12 volts anywhere when the gp light comes on the dash. They should receive 11-12v at gp connector when key-on cycled correct?

2.) The input voltage to the gp is different than the feedback voltage correct?
11v-12v to glowplugs?
Feedback 5-6volts?

3.) My reader wont let me view the live feedback data or manually cycle the gp to check for voltage.
Which wire can I probe to read the feedback voltage to ecu?

Found on a fourm:
(Conditions for Setting the DTC)
•The glow plugs are commanded OFF and the glow plug feedback is more than 2 volts
or
•The glow plugs are commanded on and the glow plug feedback is not between 5 volts and 6.2 volts.

Here's a basic list of what I've found after taking some readings:

•The CEL when cleared throws an immediate p0380 pending code after cleared, Then will comeback after a few key cycles.

•All glowplugs look fairly new (possibly replaced by previous owner trying to solve issue?
• They are correct 11V for the lb7 not the lly 4.7v
•They all ohmed @1.0ohms
•All individual Wires to each GP (CA emmisions w/ individual wires NOT bus bar connections)
@ 0.6 ohms disconnected from GP
@ 1.8 ohms connected to GP (grounded)

•When leads connected and tested with a Testlight all GP'S show proper ground.
•When pinned from the GP controller side harness (4 wire plug ) each bank shows correct ground.


•Middle plug port on GP controller
(Not the harness. The controller itself with just 12v to terminal. No plugs connected)
Pins on controller from Left to Right and color wire it would go to:
0v - pink
12v - blue
12v - yellow/pink stripe
12v - yellow

This is two tests with the OLD controller and a NEW one. The new controller did NOT solve the issue.
☆both controllers show the same middle port voltage listed above (P,B,Y,Y)

OLD GP controller:
☆ (The two outter 4 pin plug ports that feed direct to glowplug wires)
•4 Outter pins: 0 volts on all 8 pins
This stays the same with the middle harness plugged in or disconnected.

NEW GP controller:
☆(The two outter 4 pin plug ports that feed direct to glowplug wires)
•4 Outter pins: 9v on all 8 pins (with NO middle harness plug in)
•When the middle harness plugged in (pink,blue,yellow/p, yellow) voltage drops to and stays at 2.5volts
•When the outter plugs to the GP controller are connected, I read NO voltage to the back side of the harness or to the GP wire connector.

• Middle port of thenGlowplug controller: HARNESS SIDE// UN-plugged.
(The middle harness going back to main harness/ecu)

•Multimeter showed ground
•Testlight showed:
Pink - Strong ground (bright light)
Blue - weak ground (dim light)
Yellow/pink stripe- no ground (no light)
Yellow -weak ground (dim light)

On the intake heater i have :
•12v to the hot side of the relay (direct from the glowplug controller 12v terminal so makes sense)
•12v to the small wires going to the relay
• 0 volts to the Other terminal output (side that feeds the intake heater wire)
•intake heater side terminal from relay shows ground when key-off.
☆ Last owner had a 5v ignition wire jumper going to it.






Its alot of info, I hope I wrote it all easily and able to understand. Any help would be greatly appreciated. I think I just read to many posts and got myself stuck in a testing loop.

I'm not sure if the glowplugs aren't coming on at all and that's throwing the code
Or
If the feedback voltage or a problem is commanding them to stay off and that's throwing the code.

A wiring diagram or if someone can tell me there the 4 signal wires go (pink,blue,yellow, yellow) would be very helpful.

Thanks for any input

 

[2004LB7]

Most problems are from the plugs themselves. You need to test and replace any bad ones. The resistance for them is quite low. Something about 0.5 ohms. I believe the feedback voltage is monitored inside the controller and then through the communication link to the ecm the feedback voltage is reported. I'm not sure there is a place to actually read what the controller sees unless you open it up and prob in there. I would use a voltage meter and test that you are getting voltage to each glowplug (this may be somewhat similar to the feedback voltage if testing at the plug) and then test the current draw of each plug. It helps to have a DC clamp meter as you can just clamp around each wire and verify each plug. The one(s) that draws less current is normally the one

 

[Dirtymaxx88]

That was my first test. As said, I have already tested them in and out if the block.
They all read at .09 - 1.0 ohms. I also believed they needed to be around .4ohms but a few other fourm post have said they may read higher (around 1ohms)

Also i have already tested for 12v at the glowplugs. I'm getting no voltage, hence the reason for making the post.
I'm trying to find out why I am not getting voltage...an input or output from the ecu.

I dont however have a amp meter so I wasn't able to test that today. Will pickup tomorrow

 

[Dirtymaxx88]

Can you tag members?
@DAVe3283
seems very knowledgeable in a post with very similar issues.

After finding his wiring diagram and this:
CAL EMISSIONS:
The 175 Amp Fuse feeds the Glow Plug Controller at M8.
And there are two voltages from the Glow Plug Controller (OUTPUTS) that are INPUTS to the Engine Control Module (ECM)
1. Glow Plug Relay Control 505 Circuit Number
2. Glow Plug Signal 506 Circuit Number

These Signals are shown on the Plug Wiring details.

ECM Connector C1 Pin 52 LT BLUE 506 Glow Plug Signal
ECM Connector C2 Pin 6 YEL 505 Glow Plug Relay Control

Can I test these wires with a multimeter and what am looking for?
Running - 5-6 volts on LT blue
Key-on (gp cycle) ignition voltage to Pink (12V?)
Key-on (gp cycle ) signal voltage to relay/controller YEL(12v?)

 

[TheBac]

Moved to LB7 section.

 

[DAVe3283]

You should have 12V coming from the middle plug pink wire. It sounds like you do not, if I am understanding your earlier tests correctly. That ultimately comes from the "FUEL HT" fuse.

Given its proximity to the IAT relay and the previous owner doing some wiring changes to that, I would be looking there.

It should be 12V with the key on, and 0V with the key off.

Sent from my ONEPLUS A6013 using Tapatalk

 

[Dirtymaxx88]

@DAVe3283
Ok thanks!

I re-tested this morning just to verify (I may have tested wrong previously)

•Key off
Harness side of middle plug (unplugged)
Pink 0 volts
Yellow 0 volts

•Key on
Harness side middle plug (unplugged)
Pink 12volts
Yellow 12volts

•Key off
Harness middle plug (plugged into controller)
Pink 0v
Yellow 0v

•Key on
Harness middle plug (plugged into contoller)
Pink 12v
Yellow (drops to 9.5v)

So...Showing 12v to the pink (power) and some voltage (9-12v) to the yellow (relay switch control)
What am I left with?

can you verify which controller should show voltage to the outter controller pins with no plugs attached the old with 0v or new with 9volts

☆:Edited (+) Added info After retesting and rereading:

The schematic shows yellow/pink is ground correct? So i should have full ground here full time k/o or k/off. Plugged in or not correct? I have no ground here at all, tracing wires as far as I can back

 

[DAVe3283]

@DAVe3283can you verify which controller should show voltage to the outter controller pins with no plugs attached the old with 0v or new with 9volts

The glow plug controller is pretty smart, and probably detects there are no glow plugs and might not send power to the pins.

It looks like the pink wire is working right. Odd that the yellow wire is dropping to 9V or so. I wouldn't think it should. You might verify the wire resistance is low (less than 1Ω) from the glow plug controller to the ECU.

This is not an issue I've encountered before, unfortunately. I attached the diagnostic table for P0380. I'd recommend following that.View attachment BlobShtml-1.pdf

Sent from my ONEPLUS A6013 using Tapatalk

 

[Dirtymaxx88]

Lt Blue wire GP signal
(Harness to ecu pin 52)
.5 ohns

Yellow wire gp relay controller
(Harness to ecu pin 6)
.5 ohms

With the middle harness plugged in/ key-on
I have:
Pink 12v
Blue 9.5v
Yellow/pink 12v
Yellow 12v

With the middle harness plugged in/ key-off
I have
Pink 0v
Blue 3v
Yellow /pink 3v
Yellow 3v



Seems I got the yellow wire to stay at 12 rather than drop voltage.

Can anyone verify that

1.) the blue wire is gp feedback voltage and is too high (9.5v) should be (5-6.2v)

2.) The yellow/pink wire is ground and shouldn't see 12v?

 

[DAVe3283]

Can anyone verify that

1.) the blue wire is gp feedback voltage and is too high (9.5v) should be (5-6.2v)

2.) The yellow/pink wire is ground and shouldn't see 12v?

1. According to the diagnostic process I posted earlier, it should never be above 5.6 V.
2. According to the schematic that I posted in the other thread that you found and posted here, C2 pin B (pink/yellow) is ground.

Since you are seeing voltage on the ground pin, I would start examining engine grounds for corrosion. G108 is shared with the glow plug controller, intake air heater, and oil level switch. I suspect it is on the left (driver's) side of the engine block. Check it is clean, tight, and undamaged.

If it is OK, start pulling the harness apart from the glow plug controller and working until you find either harness damage or the ground. You'll find something eventually. It wouldn't surprise me if the ground wire was pinched, broken, or rubbed through. Same with the feedback wire. Just check all 4 wires carefully as you pull the harness apart. Something is wrong somewhere.

 

[Dirtymaxx88]

☆PROBLEM SOLVED ☆
Wanted to leave the info and post an update for any future guys with the same problems.

Basic issue was glowplugs would NOT come on/cycle causing a p0380 code.


It turned out to be a bad ground wire on the middle (pnk/blue/ yel-pnk/ yellow )4 pin harness (yellow/pink line wire)

Easier way to test, is unplug from the controller and test the YEL/PNK wire(harness side) pin for ground. If you get no reading, you lost your ground.

The schematic shows it to ground but it gets lost in the harness under the Inatke heater relay set-up
I simply spliced in a ground and mounted it to the ground strap just behind the controller.
Re-test for ground. Problem should be solved.