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DTC - Diagnostic Trouble Codes information

P0159

Powertrain Codes

P0159 - KIA - HO2S21 Circuit Slow Response

Symptoms

- Engine Light ON (or Service Engine Soon Warning Light) - High Fuel Consumption - Excessive Smoke from Exhaust

Possible Causes

- Rear Heated Oxygen Sensor Bank 2 harness is open or shorted - Rear Heated Oxygen Sensor Bank 2 circuit poor electrical connection - Faulty Rear Heated Oxygen Sensor Bank 2 - Inappropriate fuel pressure - Faulty fuel injectors - Intake air leaks may be faulty - Exhaust gas leaks

When Detected

The P0159 code is set when the Engine Control Module (ECM) detects that the rear O2 sensor takes more time to respond between rich and lean than the specified time.

Tech Notes

Replacing the O2 Sensor 2 usually takes care of the problem

Description

The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.