Oxygen (O2) Sensor Heater
- Unplug O2 sensor connector. Using ohmmeter, measure resistance between sensor terminals. +B and HT. See Fig 1. Replace sensor if resistance is not within specification. See O2 SENSOR HEATER RESISTANCE SPECIFICATIONS table.
- 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.
O2 SENSOR HEATER RESISTANCE SPECIFICATIONS
| Application | Ohms |
|---|---|
| Non-Turbo | 5.1-6.3 |
| Turbo | 3.0-3.6 |