## PGM-FI System

#### DTC Troubleshooting (cont'd)

11-375

DTC P0139: Secondary HO2S (Sensor 2) Slow Response

1. Reset the ECM/PCM (see page 11-312).
2. Start the engine. Hold the engine at 3,000 rpm (min-1) with no load (in Park or neutral) until the radiator fan comes on.
3. Check the secondary HO2S (Sensor 2) output voltage at 3,000 rpm (min-1) with the scan tool.

Does the voltage stay within 0.3-0.8 V for 2 minutes?

YES | - Replace the secondary HO2S (Sensor 2).
NO | - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the secondary HO2S (Sensor 2) and at the ECM/PCM.