H40 - Check HO2S Heater Relay Electrical Operation

Diagnostic Trouble Code (DTC) 593 indicates that a primary Heated Oxygen Sensor (HO2S) heater circuit failure has been detected.

Possible causes:

- Damaged HO2S HTR relay

- Open VPWR circuit.

- Open in relay control signal circuit.

- Short to power in relay control signal circuit.

- Short to ground in relay control signal circuit.

- Damaged Powertrain Control Module (PCM).

- Key "OFF".

- Disconnect both HO2S. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.

- Connect Analog Volt/Ohm Meter (VOM)/Digital Volt/Ohm Meter (DVOM) test lead to VPWR circuit and negative test lead to PWR GND circuit at the to PWR GND circuit at the HO2S vehicle harness connector.

- Enter Output State Diagnostic Test Mode (DTM).

- While observing VOM/DVOM depress and release throttle several times to cycle outputs (take this reading at both HO2S vehicle harness connectors).

- Does the voltage cycle from 10.5 or greater volts to less than 0.5 volts?

Yes -- For symptom: go to H21.

For Diagnostic Trouble Code (DTC) 593: Concern may be intermittent, reconnect all components, rerun Quick Test.

No -- For DTC 593: Go to H41

For symptom: Go to H46