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 procedure to determine the problem area further in cylinder 6:
1. Spark plug - good
2. Ignition coil - good
3. Fuel injector - good. It is a 2-wire connector, so inspected both pin further. Cylinder #6 wire has 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 can't make a clue out of it to isolate the root cause further.

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 & confirm fuel injector #6 not spraying (no PCM pulse)

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 new Odyssey owner

 

The PCM grounds one side of the injector to fire it. Each injector has it's own injector driver in the PCM. It is possible you have a failed driver inside the PCM.

You could check for continuity between injector and PCM. Leave the injector plugged in. With the key on you should get the 12v supply voltage at the PCM plug for each injector. That would confirm a good wire harness. You will need to look up the pin outs for the PCM.

 

Thx Ryanthegreat1 for the assistant.

I still call the onboard computer as ECU instead of PCM (Powertrain Control Module) as the some electronic is control using pulse-code-modulation (varying pulse width) which the acronym is PCM as well. Let's use the PCM module to avoid my personal confusion, or those who are electronic background.

I am posting to see anyone know the wiring at the PCM module end of the connector where the fuel injector #6 ground wire is connecting to. I have compared this J series engine with older 1990's Honda, and realized that the control of fuel injector is still using low voltage trigger (ground) from the PCM module. My plan is same as your suggestion to check the continuity between the fuel injector's ground wiring pin with the connector at the PCM module. There are 3 big connectors at the PCM module, and the wires are enclosed in round plastic conduit (assumes the wiring color is identical), it is not productive to probe all pins (given the tight space around the PCM module area).

Meanwhile, I have resolved the random relay clicking that I heard from driver seat. After swap relay PGM-FI sub-relay (R7) with driver's accessory power socket relay (R4), I no longer get random clicking sound. Random misfire of P0300, P0301 - P0305 are gone (tested for ~ 3 min until engine warmed up). Now the remaining CEL code is P0306, which is cylinder 6 not firing.

Ref: https://knigaproavto.ru/shemy/en/hon...2003-2008.html

 

Yes acronyms with many meanings.

In the Honda world, PCM for automatics, ECM for manuals, ECU for things older than about 2000. If we are going strictly by what is published in the factory service manuals. I know what you mean if you say ECU in this case.

Sounds like you are on the right track. Time to find a pin out for your year Odyssey. Don't rely on a pin out from another model with the same engine. Honda did a lot of swapping around of configurations in this era. For $25 a day you can have access to the factory service data from Honda. If you are lucky a Honda dealership might print you out a copy. Or maybe user tech8 here will drop in and sprinkle some pin outs on you.