2000 Honda Odyssey ecu not communicating with reader

2000 Honda Odyssey - CEL came on a couple of days ago and I took it to get the code read. The reader says it can’t link up with the ecu. Tried the same reader on another car and it worked fine. The transmission was rebuilt last year (about 9 mo. ago) and I’m concerned that something was not hooked up right during the rebuild. Is this a possibility for the non-linking of the reader to the ecu? Also, last year, before the tranny rebuild, I had a reader hooked up to the ecu and it worked fine.

As a side note, the TCS light comes on sometimes after starting the car and won’t turn off. If I restart the car it will turn off and work properly. I imagine this is related, but not sure since I can’t read the code for the CEL.

Usually that means there is a lack on power going to the OB2 connector. Check the fuses and make sure they are okay both under the hood and the dash.

In the underhood fuse box check fuse 46, 15 amp to see if it’s blown.


I found that the Honda Body Shop had not tightened the neg battery cable after they repaired the hood and grill damage. That was not allowing the van to “talk” to the inspection gadget.

After the battery was connected, I had to drive the van before it could be inspected. Now I get 5 not able to test errors.

And I can’t locate the #46 fuse to check it. Here is a copy of my failed inspection notice. Any help would be appreciated.

Since the smog station was able to determine which monitors were complete, they were able to communicate with your vehicle’s computer . . . and they hook up to the same 16pin DLC you do

It’s possible that your reader simply won’t communicate with your computer . . . seen it before

Try another reader

We tried a different reader and the fuses were good.

I found an independent Honda specialist who figured out the problem. He said it was rare, but there is a glitch/fault in the computer that resets the sensors every time the engine was turned off. As a test, we drove it some in the city and some on the highway, then pulled it into the inspection bay without turning off the ignition. The van passed with flying colours. He said he sees this rarely (about 1-2 times every 2-3 years).

People have probably spent thousands of dollars trying to “fix” this problem by throwing parts at it, including the ECM…

Look at the schematic for your ECM. I bet there are two power sources feeding it. One is supposed to stay hot when the ignition is off to retain the memory. If so, trace that one to find out why it’s dead.

I agree with @TwinTurbo. The memory power lead to the ECU needs to be checked.