Multiple Electrical Problems After Body, Engine, Or Trans Work (A08120D)

MULTIPLE ELECTRICAL PROBLEMS AFTER BODY, ENGINE, OR TRANS WORK

TECHNICAL SERVICE BULLETIN

Service Information

Got a vehicle with multiple electrical problems after body, engine, or transmission work? The culprit could be a bad ground. If a ground is loose, corroded, painted over, or disconnected, it can cause all sorts of electrical problems with systems and components. Here's just a sample of what could happen:

• The audio unit or the navigation unit cuts in and out.
• Instrument panel gauge needles swing back and forth
• Power windows, power door locks, or turn signals stop working.
• System indicators come on (with or without DTCs).
• The HDS can't communicate with the vehicle.
• Wipers and washers come on with the headlights.
• The engine cranks but won't start.
• The cruise control turns off.

A bad ground can come from sloppy body shop work. Ground points aren't always masked when prepping the vehicle for painting, so you can wind up with primer and paint on the body and threads, which acts like an insulator. A bad ground can also come from earlier work on the engine or transmission, or from installation of an aftermarket accessory.

These grounds are often the culprits:

• Battery negative terminal and body ground G1
• Headlight, turn signal, wiper and washer, taillight, and brake light common grounds
• ABS/TCS/VSA ground
• PCM ground G101 on the engine
• Transmission grounds, solenoid grounds (if applicable)

To find and fix these problems, here's what you need to do:

1. Refer to the Ground Distribution section of the applicable ETM or ISIS, and look for the ground(s) that are related to the symptoms you're seeing.
2. Inspect each ground. Make sure it's got a non-anodized, cutting-type bolt; the threads aren't corroded or painted over; there's no burr washer being used; and the bolt is nice and snug. Fix any problems you find, then go to step 3.
3. Measure the voltage drop at each ground. Here's how to do it for body ground G1:

• Turn the ignition switch to ON (II), but don't start the engine. Turn on the affected electrical components along with the headlights and the rear defogger. Turn on the fan, and set it to max.
• Using a voltmeter, attach the negative (black) lead to the battery's negative post and the positive (red) lead to the body. Wiggle the battery cable, and watch the voltmeter. If the reading is 0.3 volt or less,  it's OK. If the reading is more than 0.3 volt  , inspect the battery to body ground for loose crimps, corrosion, etc. Fix any problems you find, and retest.
  Fig 1: Measuring Voltage Drop At Body Ground G1

  
  NOTE: If you're not familiar with measuring voltage drop or would just like to learn more about it, be sure to check out "MEASURE VOLTAGE DROPS TO PINPOINT PROBLEMS " in the February '02 issue of ServiceNews. You may also want to visit Online University and check out Training Module ELC33, How to Measure Voltage Drop.