Join Date: Dec 2014Location: Tucson, AZPosts: 1,478

Ignition-Off Draw (IOD) is a normal condition where power is being drained from the battery with the ignition switch in the Off position. A normal vehicle electrical system will draw from five to thirty-five milliamperes (0.005 to 0.035 ampere) with the ignition switch in the Off position, and all non-ignition controlled circuits in proper working order. Up to thirty-five milliamperes are needed to enable the memory functions for the Powertrain Control Module (PCM), digital clock, electronically tuned radio, and other modules which may vary with the vehicle equipment.

To perform a IOD Test ...
Disconnect the battery negative cable.
Set a digital multi-meter to its highest amperage scale. Connect the multi-meter between the disconnected battery negative cable terminal clamp and the battery negative terminal post. Make sure that the doors remain closed so that the illuminated entry system is not activated. The multi-meter amperage reading may remain high for up to three minutes, or may not give any reading at all while set in the highest amperage scale, depending upon the electrical equipment in the vehicle. The multi-meter leads must be securely clamped to the battery negative cable terminal clamp and the battery negative terminal post.

After about three minutes, the high-amperage IOD reading on the multi-meter should become very low or nonexistent, depending upon the electrical equipment in the vehicle. If the amperage reading remains high, remove and replace each fuse or circuit breaker in the Power Distribution Center (PDC = front & rear fuse boxes), one at a time until the amperage reading becomes very low, or nonexistent. This will isolate each circuit and identify the circuit that is the source of the high-amperage IOD. If the amperage reading remains high after removing and replacing each fuse and circuit breaker, disconnect the wire harness from the alternator. If the amperage reading now becomes very low or nonexistent, diagnose and repair the Charging System.

After the high-amperage IOD has been corrected, switch the multi-meter to progressively lower amperage scales and, if necessary, repeat the fuse and circuit breaker remove-and-replace process to identify and correct all sources of excessive IOD. It is now safe to select the lowest milliampere scale of the multi-meter to check the low-amperage IOD.
CAUTION: Do not open any doors, or turn on any electrical accessories with the lowest milliampere scale selected, or the multi-meter may be damaged.
Observe the multi-meter reading. The low-amperage IOD should not exceed thirty-five milliamperes (0.035 ampere). If the current draw exceeds thirty-five milliamperes, isolate each circuit using the fuse and circuit breaker remove-and-replace process. The multi-meter reading will drop to within the acceptable limit when the source of the excessive current draw is disconnected

When I was experiencing excessive IOD it was due to a loose connector attached to the memory module under the driver seat. Apparently loose connectors under the front seats is not uncommon due to things rolling under the seats or being pushed under the seats.
This fixed my IOD for about a week. Then it started again. Dealership traced the problem to a aftermarket security system ... which I didn't even know was installed (I'm the 2nd owner of the car). Apparently the security system was waking up during the evening and draining the battery ... so they removed the security system. They also replaced the battery due to a bad cell. Apparently the multiple deep drain cycles damaged one of the battery cells. Everything has been fine since.