2007 Honda Accord 2.2 i-CTDi – Intermittent no-start and recurring P0602 fault

[draggore]

Hi everyone,

I'm trying to diagnose an intermittent electrical problem with my 2007 Honda Accord 2.2 i-CTDi (N22A1, CN1 saloon).

I'm not particularly knowledgeable about car mechanics or automotive electrics, but I'm trying to diagnose and fix the problem myself. I've owned this car for around 13 years and I genuinely love it, so I'd really like to get it back on the road rather than give up on it.

The symptoms:

• Occasionally, when I turn the ignition key to position II, the normal dashboard warning lights do not come on. In particular, the MIL (engine management) and battery warning lights are missing - only the oil pressure light is illuminated.
• When this happens, the engine will not start.
• The green immobiliser key indicator flashes when error occurs.
• Removing and reinserting the key several times eventually restores "normal" operation.
• When the problem occurs, I can still communicate with the ECU using an OBD diagnostic scanner.

Diagnostic findings:

• Fault code P0602 (Control Module Programming Error) is stored in the ECU.
• Clearing the code temporarily removes it, but it comes back after another failed starting attempt.

Something else I've noticed while investigating:

I wanted to locate the ECU box inside the cabin, but instead of finding the expected ECU enclosure below the centre dashboard (where the radio, clock and climate controls are located), I found something that looks quite different (see attached photo).



I then checked the relays in the cabin and discovered that there are only three fitted, whereas I was expecting to find seven.



Is this normal for the 2.2 i-CTDi CN1, or could I have some unusual or modified version of the electrical system?

I've owned the car for around 13 years, so I have no idea whether this is how it originally came from the factory.

I'd really appreciate any advice, especially from someone familiar with the CN1 diesel version. I'm still learning as I go, so even basic pointers would be very helpful.

Thanks in advance!

 

[F6HAD]

The ecu in your diesel is behind the glovebox, you’ll need to strip away some trim but you’ll eventually see it. When did the problem start, and have you had the ecu re flashed (remapped) at any point?

Based on the symptoms as you’ve described them I would say it’s a bad ignition switch, or perhaps a failing main ecu power relay.. or a failing ground somewhere.

 

[draggore]

Thank you for your answer, I will look there.

I panicked a bit because all the videos out there showed the ECU location for a different model.

 

[F6HAD]

The petrol variant has its ecu bolted to the floor behind the centre console.