2006 Honda Odyssey EX, non-VCM 3.5L J series engine

I would like to know what control the PCM pulse (pull to 0V or ground) to fuel injector, as I have one out of six not spraying. I can hear random relay clicking sound from the driver seat when this is happening. Battery is fully charged to 12V to eliminate poor battery or alternator, or power rectifier. Used voltmeter to double confirm that car is consistently getting 12V when idle.

Long story:

While driving on the street, one of the cylinder suddenly not firing and throw P0300, P0301, P0302, P0303, P0304, P0305, P0306. Car loose power, but drivable as 5 other cylinders are working. The engine runs rough (less power) but able to drive, and can crank start. Meanwhile, I can hear random relay clicking sound from the driver seat when cylinder random misfiring, but the clicking takes ~ 1 min to start to act like that.

Managed to drive home, disconnected ignition coil wiring two-by-two, then one-by-one and identified cylinder 6 is not firing.

Done following swap to determine the problem area further in cylinder 6:
1. Spark plug - good
2. Ignition coil - good
3. Fuel injector - good, but cylinder #6 wire no PCM pulse, but has 12V input

I am puzzled what could cause one of the fuel injector not getting PCM pulse (to spray). I don't have the wiring diagram of the ECU/PCM but my gut feel is that it shouldn't be bad wiring as the cylinder #6 suddenly stop firing while driving. Fuel injector wire doesn't go under the car, so it is not possible that I drive through something that cut it.

The engine bay is clean, no mouse, not full of walnut, no engine swap, no track modification, but a regular driver.

Any help will be useful. I have been struggling for 3 weeks to narrow down to cylinder #6 fuel injector PCM signal wire at the fuel injector, and but make a clue out of it.

Does disconnecting any sensor wiring able to force all fuel injector to trigger (turn on & spay)? This could eliminate faulty PCM/ECU, and focus in the wiring, or someone can tell me which pin to probe in the ECU/PCM (among 3 wiring harness) as I have a meter to perform resistance test (to confirm cable wiring is good).

Attached a picture where I put a paper tower below a bank of fuel injectors while crank to confirm fuel injector #6 is not spraying. The test is re-done by swapping it with the next injector to confirm the injector itself works fine. Another voltage test is done but not shown but connected to each of the fuel injector connector (against battery ground) to confirm the power wire has 12V

Paper tower to test fuel injector not spraying

Other though:
1. Crankshaft sensor defective - unlikely because dashboard tachometer (shows RPM) is able to show reading as I press on gas pedal. No CEL for this sensor. As far as I know from older Honda, the sensor only detect the 1st cylinder TDC (top-dead-center), so it should not affect cylinder #6, but will be all
2. It is consistently no fuel at cylinder #6's fuel injector, so it is unlikely due to broken camshaft sensor. I will assume broken camshaft sensor won't start the car, or random misfire. No CEL for this sensor. As far as I know from older Honda, the sensor only detect the 1st cylinder TDC (top-dead-center), so it should not affect cylinder #6, but will be all
3. Random relay clicking that I heard from driver seat must means relay is soft failing. How could that leads to consistently fuel injector #6 not getting PCM pulse signal?

From Odyssey owner

 

Hi members,

Got the fuel injector wiring from other Odyssey forum, I am sharing it here in this forum to help others.

All fuel injector wires are located in the center PCM module connector, which Honda label as connector B. In following table, B9 (female connector B, pin 9).

All Honda manual said jump OBDII connector pin 4 (HDS) and pin 9 (SCS) (HDS and SCS), while OBDII pin #4 is ground.

For those who didn't follow, all these wires from fuel injectors pin #2 going into PCM module. The PCM module will ground them when pulse and turn on the fuel injector. I am trying to confirm wiring connectivity between fuel injector and PCM module, so I can perform a voltage test (should show 12V), and connectivity test (should show 0 ohm).

 

Further compare of fuel injector connector #6 voltage with #5 when turn the key to ON, other injector connectors are 0V, while fuel injector #6 is 7V. Based on this diagram, PCM connector B (middle), pin 9 (B9 in above diagram) is partially leaking current.

In other word, the PCM is damaged. Going to get a used unit to confirm. It is < CAD$100 to ship from eBay US

 

Final update:
Part Number: 37820-RGL-A73
Part Description: 2006 Honda Odyssey EX PCM module

1. Received CAD$65, USD$50 PCM from eBay US, with shipping cost included
2. Problem:
2.1. Fuel injector #6 is not spraying
2.2. Fuel injector #6 is constantly giving 7V, and not pulsing
2.3. Noid light is constantly lights up, but unable to reliably shown its voltage, so needs to fallback to voltmeter
2.4.Subsequent test damaged the fuel injector relay #2, which is actually a fuel pump relay (Honda blue relay manufactured by either Mitsuba (old) or Denso (new))
2.5. When turn key from OFF to ON, fuel pump relay is getting 7V for 2 sec, then 12V constantly
2.6. DTC code P0300, P0302, P0303, P0304, P0305, P0306 (called P030X in general), which means 5 out of 6 cylinders are randomly misfire
3. Troubleshooting attempt #1 - random misfire:
3.1. Disconnects spark coil one-by-one to narrow down which cylinder is not firing
3.2. Rouge engine idle is not obvious, and needs to disconnect spark coil two-by-two
3.3. Narrowed down to cylinder #6 that is constantly not firing
3.4. Not intermittent cylinder misfire. It is cylinder #6 constantly not firing
3.5. Swap spark plugs of cylinder #6 with #5. Cylinder #6 constantly misfire
3.6. Swap fuel injector #6 with #5. Cylinder #6 constantly misfire
3.7. Measures voltage of fuel injector #6 female connector (2-wire). Getting constant 7V
3.8. Measures pin 1 of above connector with battery ground, and confirms it is getting constant 12V when turn key to ON. No issue with pin 1
3.9. Measures pin 2 of above connector with battery 12V, and getting constant 12V when turn key to ON. It should be 0V
3.10. Checked online Honda Odyssey manual to trace the pin 2 wiring of above fuel injector #6 and confirmed that it goes directly to PCM module in engine bay. No fuse. No relay. No connection to other parts. It is connected to middle PCM module connector, labeled connector B, pin 9 (row 1)
3.11. Turn key to OFF. Measures fuel injector #6 pin 2 wiring with PCM connector B pin 9 to confirm wiring connectivity. Resistant is 0 ohm, so confirmed that the Honda wiring diagram is truth & valid
3.12. Turn key to ON. Repeat 3.11 above to confirm behavior of 3.7 and getting constant 7V. Confirms PCM problem as PCM connector B is not even connected
4. Troubleshooting attempt #2 - no fuel in fuel line as PCM module damaged the blue fuel pump relay few days later:
4.1. Disconnect plastic fuel line connector, and turn the key. No fuel spray out from fuel line
4.2. Disconnect blue fuel pump relay, and test with 9V battery against pin 1 & 2. Relay is not making ticking sound (turn on). Confirmed relay broken. Relay spec ref https://omronfs.omron.com/ko_KR/ecb/...df/en-g8hl.pdf
4.3. Buy a new Denso relay from Honda dealer for CAD$70. Replacement relay is broken as well. Dealer gave another free replacement
4.4. Without fuel pump relay, jumper pin 1-2 together to mimic relay turn on. Turn car key to ON, and fuel line is delivering fuel
4.5. Measures resistant against relay pin 1-2 with broken Mitsuba relay -> 57 ohm. Measures resistant against broken new Denso relay -> 80 ohm. Measures resistant against broken new Denso relay -> 90 ohm
4.6. Reverse ohmmeter probe and measure again pin 1-2 and still get the 0.2 ohm different for the good relay. So regular/cheap ohm meter might not able to use ohmmeter as an accurate way to detect relay failure. 9V battery test is more reliable
4.7. Put jumper cable between relay pin 3 & 5, then turn key to ON. Confirms fuel is delivered to fuel line in engine compartment
4.8. Installed new and working Honda Denso relay with broken PCM module, relay won't turn on
4.9. Measures voltage of relay pin 1-2 in fuse box. Got 7V for 2 sec, then constant 12V
4.10. Measures pin 2 of fuse box relay against body ground, and gets constant 12V when key is ON. No issue with other relay and fuse
4.11. Pin 1 of relay is going directly to PCM module, so another PCM pin is broken
5. Summary of PCM damaged:
5.1. Fuel injector #6 - PCM cannot ground it, and shown constant current leak and shown 7V
5.2. Fuel pump relay (blue) - PCM cannot ground it, and gives 7V when relay suppose to turn on, then constant 12V when relay suppose to turn off (after turn key to ON)
6. Swap in a used PCM module and both issue resolved
6.1. Fuel injector is pulsing when turn the ignition key
6.2. Blue fuel pump turn on for 2 sec, then turn off which is normal behavior

Pending action:
1. Send the good PCM module to write VIN into it so that the car can work (immobilizer)
2. Mileage, and key might needs to copy over from broken PCM module

In PCM part number, found there are 3 different parts, with the later module's pin out is not compatible with my 2006