OD light flashes for first 5 min of driving

Hi

Lurker but now need help! I've got a 2000 windstar 3.8. 2 days ago the starter went and I replaced it. Starts fine. Has 135k on it. Changed trans fluid at 100k. No problems shifting, fluid smells, looks good. Currently have a PO 174 coming up and have ordered the kit from 1A auto to do the repair. The valve cover is the old style. I need help with this intermittent flashing overdrive light though. It has just started since I replaced the starter. Only flashes for about 5 minutes after starting, then goes away. Restart, it flashes again. I happened to be at the dealer today and the service guy told me that "it could be a lot of things".

Anyone have any ideas?

Piper

The flashing O/D light is an indication that the PCM has detected a problem in the transmission. Mine flashed when the Velocity speed sensor came loose, and it also flashed when my main seal began leaking, I believe due to low hydraulic pressure.

I took mine to a transmission shop after the leak for a quote on repair and they read the code at that time. They found a code indicating a torque converter clutch problem. The Autozone/Advance Auto code reader reported the problem with the velocity speed sensor.

See if you can get any codes from the PCM. It should have information on why it blinks stored in memory.

You will likely need to have a dealership or shop read the code(s) indicated by the flashing O/D light.
The flashing light is an indication that a problem has been detected with the transmission, and the codes that cause this light to flash are not in the OBDII generic set of "P" codes, so a more specialized code reader is needed than the Generic "P" code readers that you can buy or that the auto part stores use to read the codes.

Having the codes read with the correct equipment will save you from a lot of guessing.

The fluid should be changed AT LEAST every 30K miles, so you are due for that as well.
Your vehicle calls for a fluid that meets the Mercon V specification, and that is what MUST be used.
Do NOT use Mercon SP fluid.

Today I went to the local tranmission shop (which has a fantastic reputation BTW). Their code reader was able to pull about 4 codes off the computer. Anyway, the long and the short of it is that my alternator is only barely charging the battery. The mechanic at the shop felt that as the transmission is looking for a better voltage to operate the electrical components that's why the od light is flashing. Once the van is moving a bit and the charging increases, albeit it only a bit, the voltage is met and the light turns off. I know that my battery has been low and have had to do a couple of jump starts. I had planned on replacing it but now with the alternator as prime suspect it gets done first. So, I just bought a new alternator to replace tonight. I'll keep you all posted.

Piper

I would check out the battery, as a weak battery places a extra load on the alternator....and can cause it to fail.

Yes, a low battery, dirty connections, etc can cause all kinds of electrical / electronic issues.

Just wanted to let everyone know that I had the OD light flashing on my 99 LX and it turned out to be the TRS (Trans Range Sensor).
It was easy to replace. Once replaced everything is good.