ECM issue?

CKRAZE

MEMBER
2004 HONDA ACCORD
3.0L
V6
2WD
160,000 MILES

Transmission stopped working. Replaced with remanufactured transmission.

Car sat for about two months waiting for a new transmission.

When I got the car back from the shop there was a check engine light on. ODB2 code was P0453.

Discovered squirrel had chewed through the wire for the EVAP canister vent shut valve connector. Installed new connector pigtail.

Started car and check engine light went off and no codes.

CEL came back on about a minute later. Trouble codes are now P0970, P0966, P0962.

Additionally, the brake indicator light, the ABS and TCS lights now remain on.

The engine was not idling smoothly and when I put my foot on the brake pedal the car stalled but kept running. I turned on my headlights and the car died.

When I tried to do a restart, I heard a fast-clicking noise as though the Bendix gear was not engaging due to a low battery condition. Took the battery out and tested it and it tested fine but charged it overnight anyway.

Next day the car started and ran normal, but all of the lights remain on

It was at that point that I realized that I should go back and check the wiring and noticed that the pigtail connections were reversed.

I changed them to the correct way and reinstalled.

Car started fine so I cleared the codes. Reader said no issues were found but CEL still on as well as other brake related lights stayed on.

Ideas?

I do not have an engine computer reader I just have an ODB2 reader, the FIXD brand.

Final note, after the car died when I turned on the headlights, my ODB2 reader said that it could not connect to the car and said “ Low voltage, is the car on and running “? That only happened one time and it was before I recharged the battery but the battery was showing 12.4 V when I removed it and 12.6 when I reinstalled it.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

First, I need you to confirm the alternator is doing its job. If the voltage is dropping off when the engine is running, it can cause electrical issues.

Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Next, what brake lamp is on? Have you checked the fluid level? Also, is the ABS or traction control light on?

Let me know. Also, I may have to recommend having the can-bus scanned for codes that may be stored in other modules. The idea of the brake light being on can be a damaged wheel speed sensor, low fluid, or there could be an issue with a transmission speed sensor, and so on. Without checking for other codes, it will become a guessing game.

Let me know as much as you can that may help me. For example, have you checked if any wiring to wheel speed sensors may have been damaged?

Let me know.

Joe

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Friday, January 6th, 2023 AT 10:33 PM

CKRAZE

MEMBER
2 POSTS

Thanks for the feedback. I wanted to wait a few days to reply since I had decided to give the dealership a shot at diagnosing the car.

After the Honda Dealership had it for 4 days they gave up and said "come and get it, it won't connect to our computer". They pulled the port out of it's socket to - I guess - get a better connection? Didn't replace it of course.

I put it back, and after some internet digging, checked fuse 18. It was blown. Replaced fuse 18 and all the lights went away except the CEL.

CEL shows 5 codes. Three transmission ones and 2 related to the EVAP system.

They are:
P0962 A/T Clutch Pressure Control Solenoid Valve 'A' Circuit Low
P0966 A/T Clutch Pressure Control Solenoid Valve 'B' Circuit Low
P0970 A/T Clutch Pressure Control Solenoid Valve 'C' Circuit Low
P0453 EVAP Canister Vent Shut Valve Control Circuit Low Voltage
P0498 Fuel Tank Pressure Sensor High Voltage

Fuel tank pressure sensor is brand new.
EVAP Canister Vent Shut Valve is brand new.

Definitely have a parasitic draw happening. Over 4 days battery voltage dropped an average of about.75V when connected to car.

When disconnected voltage did not drop.

Drove car 130 miles after resetting the ECU. CEL still on with same codes. The battery went from 12.4v to 12.77v during that drive so not convinced alternator is the issue.

Having said that, I'm currently doing an overnight parasitic draw to check the alternator by leaving the battery connected but disconnected the alternator.

BTW, car ran flawlessly for those 130 miles. We have some pretty hilly terrain here and I made sure I worked the transmission gears as part of the 130 mile trip.

Suggestions as to how to troubleshoot these codes?

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Tuesday, January 17th, 2023 AT 7:02 AM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

Since the codes are related to low voltage, start by checking the connectors on the transmission itself. Make sure nothing is damaged, loose, corroded, or broken.

Now I do have a question. With the engine running, the voltage should have been higher. If you performed the test I listed above, it should have at least been in the 13v+ range.

Regardless, let me know if disconnecting the alternator makes a difference.

Take care,

Joe

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Tuesday, January 17th, 2023 AT 5:58 PM