Cranks but no start

DANIEL26003

MEMBER
2006 HUMMER H2
6.0L
V8
4WD
AUTOMATIC
140,000 MILES

Several days ago the truck would not start. I checked the fuel pressure with tester and pump showed no PSI. I removed and replaced fuel pump with sending unit and I got PSI back. Shows between 55-60 PSI on pressure tester. After installing turned truck on and vehicle ran for two minutes and shut off as if power was cut off. I started truck back on and truck ran for about two more minutes and just cut off. Radio was still on so I know that I still had ACC. I still have the fuel pressure tester connected to fuel rail and it still shows fuel pressure is there. So I know it's not the fuel pump cutting off. I removed a connector going to fuel injector and checked for voltage while cranking up and it read 4.86 volts to almost 5 volts while cranking. I figured it was a bad crankshaft position sensor so I removed and replaced it and attempted to start the truck but it still only cranks but no start. The part states that I have to relearn it. I figured that the truck would of started after changing the crankshaft position sensor. Does the truck have to turn on in order to perform relearn procedure? I'm stumped and don't know which direction to go from here, any advice would be highly appreciated. Thanks

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi and thanks for using 2CarPros.

First, take a look through this link. It discusses the most common causes for a crank / no start condition.

https://www.2carpros.com/articles/car-cranks-but-wont-start

If pressure is good and you have an injector pulse, I need you to check for spark to the plugs. Here is a quick link:

https://www.2carpros.com/articles/how-to-test-an-ignition-system

To answer your question related to relearn, yes. The engine needs to run.

Now, if you find there is no spark, I think I know what is wrong. All of the coil packs have a common ground. The ground wire is black and is part of the wiring harness on the intake for the coil packs. The ground location is on the top left rear of the engine block. See the schematic I attached:

Locate the ground and check it's condition. Don't be surprised if the connector falls apart when you move it. Also, although the ground may be bad, it can still show continuity when checking. However, the ground can no longer take the current needed to fire the coils.

If you find the wire is good at its mount on the engine, work backwards from that point. If none of the cylinders are firing, it may be broken between the mount and the first coil pack splice.

Just FYI... Here is the relearn for the crankshaft position sensor.

CKP SYSTEM VARIATION LEARN PROCEDURE

1. Install a scan tool.
2. Monitor the powertrain control module (PCM) for DTCs with a scan tool. If other DTCs are set, except DTC P0315, refer to Diagnostic Trouble Code (DTC) List - Vehicle for the applicable DTC that set. See: A L L Diagnostic Trouble Codes ( DTC ) > Diagnostic Trouble Code Descriptions
3. Select the crankshaft position (CKP) variation learn procedure with a scan tool.
4. The scan tool instructs you to perform the following:
1. Accelerate to wide open throttle (WOT).
2. Release throttle when fuel cut-off occurs.
3. Observe fuel cut-off for applicable engine.
4. Engine should not accelerate beyond calibrated RPM value.
5. Release throttle immediately if value is exceeded.
6. Block drive wheels.
7. Set parking brake.
8. DO NOT apply brake pedal.
9. Cycle ignition from OFF to ON.
10. Apply and hold brake pedal.
11. Start and idle engine.
12. Turn A/C OFF.
13. Vehicle must remain in Park or Neutral.
14. The scan tool monitors certain component signals to determine if all the conditions are met to continue with the procedure. The scan tool only displays the condition that inhibits the procedure. The scan tool monitors the following components:
- CKP sensors activity-If there is a CKP sensor condition, refer to the applicable DTC that set.
- Camshaft position (CMP) sensor activity-If there is a CMP sensor condition, refer to the applicable DTC that set.
- Engine coolant temperature (ECT)-If the ECT is not warm enough, idle the engine until the engine coolant temperature reaches the correct temperature.
5. Enable the CKP system variation learn procedure with a scan tool.
6. Accelerate to WOT.

IMPORTANT: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine responds to throttle position after the learn procedure is complete.

7. Release when the fuel cut-off occurs.
8. Test in progress
9. The scan tool displays Learn Status: Learned this ignition. If the scan tool indicates that DTC P0315 ran and passed, the CKP variation learn procedure is complete. If the scan tool indicates DTC P0315 failed or did not run, refer to DTC P0315. If any other DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for the applicable DTC that set. See: A L L Diagnostic Trouble Codes ( DTC ) > P Code Charts > P0315 See: A L L Diagnostic Trouble Codes ( DTC ) > Diagnostic Trouble Code Descriptions
10. Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.
11. The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether DTC P0315 is set:
- A CKP sensor replacement
- An engine replacement
- A PCM replacement
- A harmonic balancer replacement
- A crankshaft replacement
- Any engine repairs which disturb the CKP sensor relationship

Let me know if this helps or if you have other questions.

Take care,
Joe

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