2. O2 Heater Control Circuit Shorted To Ground

With the ignition off.

Disconnect the PCM harness connectors.

NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between ground and the O2 Heater Control circuit.

Fig 1: Measuring Resistance Between Ground & O2 Heater Control Circuit

Courtesy of DAIMLERCHRYSLER CORP.

Is the resistance below 100 ohms?

Yes >> Repair the O2 Heater Control circuit for a short to ground.
See POWERTRAIN VERIFICATION TEST - VER 2 .
No >> Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary. Replace and program the Powertrain Control Module. See ELECTRONIC CONTROL MODULES article.
See POWERTRAIN VERIFICATION TEST - VER 2 .