P1607 when car is cold, honda odyssey

With the recent cold spell around Houston Area, my Honda Odyssey is giving me a P1607 (PCM malfunction code) every time when the car is cold.

It is a 2000 odyssey with 125K miles on it. I have never experienced this until recently when the temperature is close to freezing. When it has the P1607 code, It can not shift gear, but after drive around a while and when the engine is warmed up, I can clear the code and everything backs to normal.

Is the PCM really bad? I am leaning to think that some other things may not be functioning correctly when the temperature is low, what would these be?


A Web search had these results: 1. Let a Honda dealer reflash the PCM (engine computer).
2. Replace the PCM.
3. Check the power voltages to the PCM. Backprobe the terminals at the PCM to obtain the voltages. Use a pin-out PCM chart to identify which ones supply power to the PCM.

I wonder why your car is setting the proprietary Honda (PCM Internal fault “A” code) and not the generic (and more serious) P0600 thru P606 codes? These generic 600 series codes most often mean a replacement is due.

I would ressearch what fault “A” means

When it was faulty during the day, the battery is reading 12.5V. So far in the garage, the battery is 12.87V and no code yet. I am leaning towards the coldness putting a strain on the battery. However, this is a 4 month old battery. The only thing is I only drive 20 miles a day locally in weekdays.

You’ve got the idea! You want to make sure that the power supply voltage going into the PCM are within 1/2 volt of the battery voltage. You won’t know if they are until they are checked with a voltmeter.

Thanks. What if it is indeed low voltage to PCM power, what could be the possible cause?

Voltage drops can result from poor contact of wire terminals within electrical connectors. Grounds need to be checked. Grounding wire connections (to frame, body, engine) can have resistance which hampers current flow through the circuit.

This morning the battery is 12.59V and the code is back on. Looks like I need to check what you suggested first. Thanks

Power (very close to battery voltage, hopefully) goes into the engine computer (PCM) over 3 or 4 wires. One wants to insure that the voltage on each power wire, measured AT the PCM, compares, closely, to the battery voltage (measured AT the battery).
One can measure the voltage by back-probing each wire with a multimeter. [Don’t puncture the wires to take the measurements; but, slide the multimeter test lead along the wire to contact the terminal.]

Now the weather is warm and the problem is no longer with the car. Do you think I can still find out by measuring the wire voltage? Thanks

I have a 01 CL with the same 1607 code only on cold mornings here is Houston. What was the fix for your odyssey

I am around Houston too. The p1607 went away since last time I posted because the weather warmed up. It did not come back until the weather got cold in December again. This time it took me around 10 min to get warm up and seemed getting worse. I even learned to drive with the code on, just have to time the local traffic and restart the engine at red light.

I tested it repeatedly, and it is the temperature. Like take the PCM inside and keep it warm and install it in the morning just before I go (and it works). I suspect there must be some thermo stress involved with the circuit board. Finally, I bought a used PCM from Ebay and had the dealer (1hour labor, they are the only one can do it) reprogram my keys. It’s been 2 month and code free. Glad I did it because the past couple months have been unseasonally cold. Try your luck with used PCM first. You can install the PCM, the engine won’t start because the key code is incorrect. But you can make sure the new PCM won’t throw the code and then take it to dealer. The weather is getting better, so maybe next year? :slight_smile: