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P0051 HO2S Heater Control Circuit Low (Bank 2 / Sensor 1)

AutoHex Online Help: Hyundai SANTAFE(CM) 2012
Component Location
General Description

The normal operating temperature of the HO2S(Heated Oxygen Sensor) ranges from 350 to 850°C(662 to 1562°F). The HO2S heater greatly decreases the amount of time required for fuel control to become active. The ECM provides a pulse width modulated control circuit to adjust current through the heater. When the HO2S is cold, the value of the resistance is low and the current in the circuit is high. On the contrary, if the temperature in the resistor of the sensor rises, the current drops gradually.



DTC Description

If the ECM detects short to ground or open in heater under detecting conditions, ECM sets P0051.

DTC Detecting Condition

Item

Detecting Condition

Possible Cause

DTC Strategy

Detects a short to ground or open

Poor Connection

Open in Power Circuit

Open or short to ground in control circuit

HO2S(B2/S1)

ECM

Enable Conditions

No disabling Faults

Engine Running

11V = Battery Voltage = 16V

Threshold value

Short to ground or open circuit

Diagnosis Time

Continuous (More than 5 seconds failure for every 10 seconds test )

MIL On Condition

3 Driving Cycles

Specification

Heater

Resistance (?)

3.3 ~ 4.1[20?(68?)]

Diagnostic Circuit Diagram
Signal Waveform & Data

Fig.1) The signal waveforms of front HO2S(the upper) and heater(the lower) at idle (chassis ground used)

Fig.2) The signal waveforms of front HO2S(the upper) and heater(the lower) at idle (sensor ground used)

Fig.3) The signal waveforms of rear HO2S(the upper) and heater(the lower) at idle (chassis ground used)

Fig.4) The signal waveforms of rear HO2S(the upper) and heater(the lower) at idle (sensor ground used)

Fig.5) The Normal data of HO2S heaters at idle (approx. 0.5A)

Fig.6) The data of HO2S heaters at open condition in HO2S(B2S1) circuit (0A)

The output voltage of front HO2S is changed continuously accroding to air/fuel ratio, ECM controls fuel amount based on this value. Preheating is necessary for HO2S normal operation. Therefore heater unit is installed in HO2S, ECM can control air/fuel ratio with the output signal of HO2S simultaneous with engine run by reducing preheating time. ECM controls heater with duty cycle. HO2S' power source is main relay and ECM operates heater by ground control.