brigman262

Looking for help on a 720 code problem. After looking extensively on several forums, I haven't found a clear solution.
97 accord 2.3. 225k miles, trans is used replacement when we bought the car. Shifts and works great. One day cel came on, D4 light flashing. Replaced the OSS sensor, light back on. Checked all wiring and plugs visually, no change. Had a local import shop run tests ($400), replaced ECU (with used for obvious reasons) light back on. It s a great car worth saving. Your help would be greatly appreciated.
Has anyone been through this and what was the solution?

MAD_MIKE

What is an OSS sensor?
https://honda-tech.com/honda-accord-.../#post50701087

Don't post multiple posts about the same problem. It will confuse, or worse, annoy members to see the same question in multiple posts and you may receive confusing remedies with multiple lines of thought, sometimes incorrect.

As mentioned in the link, pull the sensor and verify it is clean, verify it is within resistance specs and verify the wiring is indeed intact. Check for corrosions/damage/breaks in the harness and connectors.

brigman262

Mike, you lost me man. Not sure what your scolding me about multiple posts on the same problem??
The OSS sensor is the output shaft speed sensor on a 97 accord.The other diagram in your link shows 2 sensors...NM and NN I believe?? I dont think that diagram is for a 97 accord 2.3 auto trans. Its not looking familiar anyway.
So the best solution is to test the ohms readings at the ecm and the sensor? If i've already done that , and replaced both , what next? That my problem.

MAD_MIKE

You have started this thread on your problem, and also posted in an older thread with regards to the same problem. You may get confused/conflicting answers from members, and not all members will check every post you make. Thus, you may end up very different, and confusing, answers.
90-97 USDM Accords, and related PGM-FI models, used the H4A automatic. Which used three shaft sensors. NC(countershaft), NM(mainshaft), and VSS(vehicle speed(speedometer) sensor). I am not sure of what sensor you are referring to when you state 'OSS'.
Location, location, location.
Where are you located, or better, where is the car originally from?
Most members here are in the U.S.A. There is no such thing(from the factory) as a 1997 2.3 Accord in the US.
90-93 = CB Accord (2.2) H4A automatic
94-97 = CD Accord (2.2 & 2.7 V6) H4A automatic
98-02 = CG Accord (2.3 & 3.0 V6) M6HA Automatic

Different markets had different chassis types, or overlapping years.
https://en.wikipedia.org/wiki/Honda_Accord

The VIN or door sticker should have the chassis number in it, CB/CC/CD/CE/CF/CG/CL with a number after designating year/model type.
https://en.wikibooks.orghttps://en.w...onda/VIN_Codes

Submodel would also help. Do you have some po-dunk Greek Accord VX or Japan Accord Wagon SiR?

If your right side cover does not look like the H4A, then your car may have the M6HA family of transmission. There should be a barcode sticker with a four letter code, e.g. 'AOYA', 'MPJA', 'BAXA', 'MGRA', etc. That will properly identify what trans you have.
Fairly sure the resistance is the same, but it would be best to nail down what you actually have.