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Chris (aka- Moose)
Chris (aka- Moose), GMC Technician
Category: GM
Satisfied Customers: 47637
Experience:  16 years of experience
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Need experienced 01 6.6l duramax mechanic with electrical

Customer Question

Need experienced 01 6.6l duramax mechanic with electrical skills. Truck was fogging diesel while idling, but ran fine while driving. Replaced all injectors and fuel lines, bled system, no start. I am not getting any injector command on scan tool. Shows good fuel pressure while cranking, but obviously won't start if injectors won't open. New cam and crank position sensors and reluctor ring was solid. Where does the ficm get it's signal to command injector to open?
Submitted: 1 year ago.
Category: GM
Expert:  Juan Crespo replied 1 year ago.

The FICM gets its signal from the PCM. As you describe it, it sounds like your anti-theft system has been activated and is currently not allowing the engine to start.

The Passlock(tm) system is designed to prevent vehicle theft by disabling the engine unless a mechanical key is used to correctly engage and rotate the Passlock(tm) lock cylinder. System components include ignition switch, Passlock(tm) lock cylinder, Passlock(tm) sensor, Passlock(tm) module and Powertrain Control Module (PCM).

Do you have a second passlock key that you can try? If not, you would need a scan tool capable of communicating with the various modules in the truck to see what's happening.

Expert:  Juan Crespo replied 1 year ago.

Thought you might need this:

1. Turn ON the ignition, with the engine OFF.
2. Attempt to start the engine, then release the key to ON, vehicle will not start.
3. Observe the SECURITY telltale. After approximately 10 minutes, the telltale will turn OFF.
4. Turn OFF the ignition, and wait 5 seconds.
5. Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes. The vehicle is now ready to relearn the Passlock Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK.
6. Start the engine. The vehicle has now learned the Passlock Sensor Data Code and/or password.
IMPORTANT: The vehicle learns the Passlock Sensor Data Code and/or password ***** the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
7. With a scan tool, clear any DTCs if needed. History DTCs will self clear after 100 ignition cycles.

Customer: replied 1 year ago.
Juan, key on, there is no security light, my research shows no passlock on this truck. Also no "+" on the key to show it has a resistor. Please tell me about the security telltail.
Expert:  Juan Crespo replied 1 year ago.

If, as you say, there's no passlock on that truck, then there's no Security telltale nor, if the truck has the optional Message Center, the word SECURITY will be displayed.

In any case, I can't see where anything you've done would cause the engine not to start. So, the only way to find whether or not there is communication between the PCM and the FICM or if there is something else preventing the signal from getting through is with the help of a Tech-II or equivalent scan tool.

Customer: replied 1 year ago.
I do have a scan tool, that's how I know there is no injector command as stated in original message, I need to know which wires to probe to know if problem is in the ecm or ficm.
Expert:  Juan Crespo replied 1 year ago.

I'm sorry if I didn't explain it better: the computers in your truck communicate with one another through a serial data bus; probing these bus wires with anything but a scope won't show us much - even with a scope, all we'd see is a serial data signal if one was there. We still wouldn't know what that serial data meant.

What we need is a dealer-level scan tool such as the Tech-II that can communicate with all the modules in the truck, read serial data and interpret it for us. It can also tell us if any of those modules is preventing others from getting the signals they need to go to work. I wish the carmakers had made it easier for us to work on these vehicles, but they just want to push us back to their dealers where they can charge us whatever they want

Customer: replied 1 year ago.
Juan, So what your saying is you can't help me right?
Expert:  Juan Crespo replied 1 year ago.

I'm afraid I would have to agree with you, since you don't seem to have access to the tools you would need to use in order to follow my intructions. But wait, another expert on the site might know what to do. I'll opt out so others may try. Please don't reply until another expert responds or the site will cycle the request back to me.

Expert:  Chris (aka- Moose) replied 1 year ago.

Welcome, I'm Chris (aka Moose). Experts aren't employees / agents of Just Answer. We are independent service providers using the Site to sell their Expert knowledge to Customers. I strive to provide EXCELLENT 5 STAR service, let me know what's needed from me so your pleased.

  1. The previous tech has opted out. Would you like me to help?
Customer: replied 1 year ago.
Expert:  Chris (aka- Moose) replied 1 year ago.

So your getting no trouble codes?

Are the cam and crank sensors getting an accurate signal back to the PCM?

Customer: replied 1 year ago.
as to codes, p0340 cam sensor or circuit. Sensor has ok volts(10.6), good ground and frequecy when tested aprox. 4" from sensor. not sure what pin or connector to check at ECM.
Expert:  Chris (aka- Moose) replied 1 year ago.

Using your scan tool and cranking the engine are you getting a CMP and CKP signal that is consistent and just about identical?

Customer: replied 1 year ago.
Using a ds 708. There is only cam reference signal missed(0) and no CKP signal( shown on this scanner) also no rpm reading i.e. (0) during cranking.
Expert:  Chris (aka- Moose) replied 1 year ago.

Your scan tool may not be sophisticated enough. Do you have the ability to try another. We need to confirm the computer is getting these signals to figure out why your getting no injector signal.

Customer: replied 1 year ago.
If you can tell me wich pins to probe at the ecm, I could at least verify a signal to the ecm. This truck has 380000 miles on it and it could be bad wire.
Expert:  Chris (aka- Moose) replied 1 year ago.


low reference pin 21 YE/BK

CKP signal pin 12 LB/WH

12 volt reference pin 2 LG


CMP signal pin 73 BR/WH

low reference pin 61 PK/BK

12 volt reference pin 39 RD this is the only one in connector 2 at the ECM

Customer: replied 1 year ago.
continuity to ecm checks good(CKP, CMP), still no rpm and p0340 code returns after clearing. I could get another scanner to check cmp and ckp, but if they read 0 as I assume they will, then it looks like ecm is the culprit. FICM will not command injectors if it doesn't see RPM, correct?
Expert:  Chris (aka- Moose) replied 1 year ago.

Your correct if the FICM is not getting a signal, it will not pulse the injectors.

Expert:  Chris (aka- Moose) replied 1 year ago.

Hello again Chris here,

1) When customers come to Just Answer the website and the experts want them to have a great 5 star experience.

2) We also want them to be so pleased that they come back for future needs.

3) I have the feeling you were not pleased with my help and or need me to help more. If so please do reply.

4) I have an option to upload diagrams, repair guides, find a repair facility, or call you if that would help.

Thanks Chris

Customer: replied 1 year ago.
Hi Chris, yes I would appreciate any additional help. Have you ever heard of air in the fuel line causing a po340 code? Also could you please walk me thru the fuel bleed process as you know it? Seems simple, but maybe I'm missing something.
Expert:  Chris (aka- Moose) replied 1 year ago.

A fuel issue that may be causing a misfire could cause a incorrect CMP and CKP code to store from the engine speed abruptly changing. There is a priming step, not a bleeding step.