Oxygen (O2) Sensor Heater (2.5L Only)
- Unplug O2 sensor connector. Using ohmmeter, measure resistance between sensor terminals. +B and HT. See Fig 1. Replace sensor if resistance is not within 5.1-6.3 Ohms.
- A Code No. 21 is also an indicator of a problem in O2 sensor circuit. Code No. 21 will set if O2 sensor heater circuit opens or shorts to ground on HT wire from sensor to ECU.