Rick's Free Auto Repair Advice

Install a Car Battery

Install a car battery

You can’t just yank the battery cables off a car battery on a late model vehicle to install a car battery without causing some problems. Most late-model vehicles include many electronic devices that require power to maintain their “home” positions. An electronic throttle body for example, is susceptible to carbon buildup. Over time the throttle plate doesn’t close all the way and the computer adjusts for that buildup and learns a new wider “home” position. When you disconnect the battery cables, it loses that memory. After installing the new battery, your engine may not start or it may idle too high. Other electronics have memory issues as well, like the steering angle sensor for the stability control, memory power seats and mirrors, adjustable pedals, and the auto-up/down power windows settings.

image of accelerator postion sensor and electronic throttle body

The gas pedal sends electronic signals to the PCM which then tells the throttle body how far to open

The best way to avoid having to tow your car in for reprogramming is to avoid losing the memory in the first place. Here’s how to do that.

Connect a jumper battery to the OBDII port before installing a new battery

You’ll need a jumper pack or an AC-DC power converter, and you’ll need a special OBDII cable. The SOLAR #ESA30 cable is about $9. You can pick up a battery-powered jumper pack at any auto parts store or Walmart for under $50. car jumper pack

1) Turn off all electrical accessories including the blower and headlights.

2) Remove the key from the ignition.

3) Plug the cable into the OBDII port. Then plug the cigarette lighter end into the jumper pack.

4) Disconnect the negative battery cable. Then remove the positive cable and INSULATE it—it’s live. I usually throw it inside a leather glove.

5) THEN you can remove the dead car battery.

6) Lift the old car battery out, making sure you don’t dislodge the insulator on the positive terminal.

6) Clean the battery tray and all the hold-down connections. If the threads on the J-bolts are corroded, clean them with a wire brush and apply a light coating of anti-seize. If the hold-down clamps or brackets are rusted, spray them with a battery acid neutralizer products. Then dry and spray with a fresh coat of paint.

7) Clean the posts on the new car battery and the cable terminals using a wire brush. Then install the car battery onto the battery tray.

8) Position the top bracket. Then install the positive battery cable first and then the negative cable. Make it a quick push-on affair—you want to avoid arcing that can damage computers. Tighten the hold-down bolts and nuts. Once the new battery is installed, you can remove the supplemental power.

This procedure keeps the PCM fully powered up and prevents it from losing all it “adaptive memory.” So you can start the engine and go without the PCM having to relearn all the values.

change car battery, install car battery

Keep memory alive with a jumper pack and OBDII adapter cable.


Need to charge your car battery? Click here for instructions

If your battery terminals are corroded, replace them. Click here to see how.

© 2012 Rick Muscoplat




Posted on by Rick Muscoplat

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