Chevy and GMC Duramax Diesel Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
About a month ago I started experiencing Cranking, no starting issues (It hits 3 times then have to quit cranking because it won’t hit again, guessing that’s when the P340 code is sent to the ECM). Last December I had a couple codes P340 and the Turbo Vane Position Sensor (don’t remember the exact code). Replaced both of them December ‘18. Now I have two glow plug codes and the P340 again. Basically if I get it started I leave it running anywhere I go because I don’t know when it will want to start if I shut it off. I loose prime on the fuel filter housing. So I rebuilt it and went a couple days and then left me stranded at work. I can prime, unhook the batteries and anything I can think of for hours and it won’t start. Leave and then come back anywhere from 1 hr to 12 hrs and it starts and doesn’t miss a beat. My RPM gauge intermittently goes out but I have a digital read out on my CTS2. But when I notice it’s at zero that’s when it won’t restart after shutting it off. I can get it started and running on ether. Thoughts are reluctor wheel? Ignition switch? Electrical wiring gremlin?
 

·
Registered
Joined
·
1,537 Posts
DTC P0340

Diagnostic Instructions



DTC Descriptor

DTC P0340


  • Camshaft Position (CMP) Sensor Circuit
Diagnostic Fault Information






Typical Scan Tool Data





Circuit/System Description

The hall effect camshaft position (CMP) sensor produces 3 ON/OFF pulses for each revolution of the camshaft. The CMP output is pulse width encoded. The engine control module (ECM) uses the CMP and crankshaft position (CKP) output pulses to determine the engine speed and position. The CMP is connected directly to the ECM by the following circuits:


  • The 5-volt reference circuit
  • The low reference circuit
  • The CMP sensor signal circuit
Conditions for Running the DTC



  • The ignition is ON.
  • The engine is turning faster than 50 RPM.
  • DTC P0340 runs continuously when the above conditions are met.
  • DTCs P0335, P0336, P0642, or P0643 are not set.
Conditions for Setting the DTC

The ECM does not see a CMP sensor signal for more than 2 seconds.

Action Taken When the DTC Sets

DTC P0340 is a Type A DTC.

Conditions for Clearing the MIL/DTC

DTC P0340 is a Type A DTC.

Diagnostic Aids

If the CMP sensor signal is lost while running, the engine will operate normally. If the CMP sensor signal is not present on start-up, the engine will not start.

Circuit/System Verification



  1. If DTCs P0642 or P0643 are set, diagnose those DTCs first.
  2. Engine running, observe the DTC information with a scan tool. DTC P0340 should not set.
  3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing



  1. Disconnect the CMP sensor.
  2. Test for less than 1 ohm between low reference circuit terminal 2 on the ECM side of the connector and ground.
    • If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  1. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 on the ECM side of the connector and ground.
    • If less that the specified range, test the 5-volt reference circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.
    • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  1. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 1 on the ECM side of the connector and ground.
    • If less than the specified range, test the affected signal circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.
    • If greater than the specified range, test the affected signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  1. Ignition OFF, connect a 3A fused jumper wire to the CMP signal circuit terminal 1 on the ECM side of the connector.
  2. Ignition ON, momentarily touch the end of the fused jumper wire to ground. The CAM signal present and the engine RPM parameters on the scan tool should change.
    • If the CAM signal present and the engine RPM does not change, replace the ECM.
  1. Ignition OFF, inspect the wiring harness for any damage, opens or shorts.
    • If the circuits test normal, replace the CMP sensor.
 

·
I'm That Guy...
Joined
·
16,681 Posts
Where are you located?

When it doesn't start does it crank? On both CTS and gauge cluster it shows 0 RPM?

When you primed the fuel system did you have air coming out or fuel immediately?

Sounds like Ron pointed you to the right direction, but curious on other details.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #4
Where are you located?

When it doesn't start does it crank? On both CTS and gauge cluster it shows 0 RPM?

When you primed the fuel system did you have air coming out or fuel immediately?

Sounds like Ron pointed you to the right direction, but curious on other details.
Located in south central Kansas.

When it doesn’t start it cranks. I can crank on it until my batteries go dead or burn the started up. *which I haven’t done*

The cluster is the only thing that goes out, the CTS shows the RPMs like it should with no problem.

Fuel immediately. Of course when I changed my filter I had air that I had to bleed out. But anytime I unscrew the bleeder screw I have fuel coming out.

I will follow Ron’s post.

Thanks!
 

·
Registered
Joined
·
7,229 Posts
There has been a few issues for some trying to rebuild the filter head, buying a new replacement might have solved one issue.
They run around $120-$150 depending on searching for the best price most include a quality filter.
When I did mine it was a new Parker with AC Delco TP3018 fuel filter.
What brand fuel filter are you using ?
 

·
Registered
Joined
·
3 Posts
Discussion Starter #6
There has been a few issues for some trying to rebuild the filter head, buying a new replacement might have solved one issue.
They run around $120-$150 depending on searching for the best price most include a quality filter.
When I did mine it was a new Parker with AC Delco TP3018 fuel filter.
What brand fuel filter are you using ?
I’m running the same fuel filter. TP3018

Hopefully today I can get in the shop and start down the list supplied above.
 
1 - 6 of 6 Posts
Top