[ronbiggs]

Just started getting a P1493 code and the Battery & CEL lights came on. Manual says "Ambient/Batt Temp Sensor Volts Too Low". Still have the original battery (235K miles).

Could it be a failing battery, or something more sinister??

[peva]

It has nothing to do with the health of the battery. It is telling the PCM what the ambient air temperature is near the battery (located behind passenger side headlight). The sensor has two wires - the ground back to the PDC and the signal wire back to the PCM. Hopefully sensor is bad or one of the two wires is shorted or open (and not a bad PCM). Check connector at sensor for the connection and corrosion.

However, your battery is overdue for replacement - again, unrelated to that code.

[ronbiggs]

Can you give me an idea of what the sensor looks like. I see a black canister shaped thing behind the headlight with a wire connector to it. Is that it? How can I check for a loose connection at the PCM?

Coincidentally, I just had the left front fender replaced today at the body shop. If that is where the PCM is, I wonder if it got loose when they did the body work?

[ronbiggs]

Found it...fixed it. Real easy. I did another search and found a thread that located the sensor very easily. It is actually attached to the front grill with a plastic clip/rivet, just to the left of center, in front of the AC condenser. Easy to remove the clip from the front, and removing the RF headlight gave easy access to change the sensor.

btw...when I switched the overhead console to the outside temp it read 154 degrees!!!! Pretty good clue that the sensor was bad.

Anyway, after I replaced it I had to reset the error codes. Just disconnecting the battery only reset the temp on the OH console. I had to do a "full" reset by disconnecting the battery, and holding the key in the "Start" position for 30 seconds (not sure where I heard that, but it seems to work). That did the trick, the CEL is off and the error codes are gone. I do have to take it for a longer drive, however, to be sure it doesn't happen again (that'll really piss me off!!)

[ronbiggs]

Went for a drive for about 25-30 miles. Just before I got back home, the damn CEL & Battery lights came back on...same code P1493!! And the OHC temp indicator went spaz-o on me too...went down to 0 degrees, back up to 100 degrees and now seems to be locked in at 94.

Wondering now if it is a BCM problem.

Anyone have any thoughts....

[peva]

Sorry I didn't state its location more accurately. Also, I said it was connected to the PCM. It goes to the BCM. I was looking at the '02 FSM (in which it does in fact go to the PCM). Must have been in a hurry.

I'd keep troubleshooting the connection at the sensor and the wiring back to the BCM. The two wires go thru 2 connectors (Violet/Light Green and Dark Blue/Grey the whole way), C114 (under left headlamp) and C103 (left side instrument panel), on their way to the BCM. Perhaps C114 got disturbed or a wire near it got damaged during the fender replacement? That would be a likely scenario.

[ronbiggs]

Thanks!! I'll give it a look.

[ronbiggs]

Went back to the body shop, and we looked at the wiring. Did not see anything obvious. The guy there said that it might be that the Autozone sensor was faulty. Got one from the dealer (ironically it was only $9 compared to $22 at AZ). Slapped that one on, and it seems ok for now. If that doesn't solve it, I guess I will get out the multi-meter and start checking the wires at the different connectors for continuity.

[ronbiggs]

Replaced the temp sensor with one from the dealer. Ran for 3-4 days with no problem. OH console temp indicator working fine as well. Guess the Autozone version of the sensor was faulty after all. Glad I didn't have to spend a lot of time chasing after a short!