P1158 MERCURY – Lack of Heated Oxygen Sensor Switches, Row 2 Sensor 2 Indicates Rich

Code P1158 MERCURY – Causes, Symptoms, and Repairs

1. Meaning of Code P1158 MERCURY

The fault code P1158 is related to the Heated Oxygen Sensor 2 (HO2S2) located downstream of the three-way catalyst. This sensor monitors the oxygen level in the exhaust gases and allows the Powertrain Control Module (PCM) to adjust the air-fuel ratio to optimize combustion.

The sensor generates a voltage between 0.1V and 0.9V:

  • Voltage < 0.45V → lean mixture (too much oxygen)
  • Voltage > 0.45V → rich mixture (too much fuel)

When this sensor does not function properly, the PCM may not be able to correctly adjust fuel injection, leading to the appearance of code P1158.

2. Possible Symptoms

  • Engine light on (Check Engine)
  • Fuel consumption issues
  • Irregular idle or loss of power

3. Possible Causes of Code P1158 MERCURY

Several factors can cause this error code:
✅ Exhaust gas leaks
✅ Faulty Heated Oxygen Sensor 2 (HO2S2) (Bank 2, downstream)
✅ Open or short circuit in HO2S2 sensor wiring
✅ Poor electrical connection of HO2S2 sensor
✅ Inappropriate fuel pressure
✅ Faulty fuel injectors

4. How to Repair Code P1158 MERCURY?

Here are the recommended steps to diagnose and resolve this issue:

🔍 Step 1: Checking Connections and Electrical Wiring

✔️ Visually inspect the oxygen sensor wiring harness and connectors.
✔️ Look for broken, bent, pinched, or corroded wires.

🔍 Step 2: Checking the HO2S2 Oxygen Sensor

✔️ Test the sensor with a multimeter:

  • Check the output voltage (should be between 0.1V and 0.9V).
  • Replace the sensor if it does not respond correctly to air-fuel mixture variations.

🔍 Step 3: Checking for Exhaust Leaks

✔️ Inspect the exhaust manifold and catalyst for possible leaks.

🔍 Step 4: Checking Fuel Pressure and Injectors

✔️ Check fuel pressure using a pressure gauge.
✔️ Test fuel injectors and replace any that are clogged or faulty.

5. Conclusion

Code P1158 on a MERCURY vehicle is often related to a faulty oxygen sensor or an electrical issue. A thorough diagnosis is necessary to avoid unnecessary part replacement. By following these steps, you can effectively identify and fix the problem.

🚗 Tip: If you are unsure about the diagnosis, use an OBD2 diagnostic tool or consult a professional.

P1158 MINI – Fuel Trim Adaptation Additive, Bank 1 Low

P1158 MINI Possible Causes

  • Air leaks
  • Faulty mass air flow (MAF) sensor
  • Faulty oxygen sensor, bank 1
  • Low fuel pressure
  • Faulty spark plugs
  • Faulty fuel injectors

How to Fix MINI Code P1158?

Start by checking the “possible causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

  • Check engine light on (or service engine soon warning light)

P1158 MINI Meaning

Short-term fuel trim (STFT) is a value that indicates how the engine control module (ECM) adjusts the factory-programmed fuel map. The fuel map is a lookup table that the controller references. This is used to determine the correct amount of fuel to inject. This amount depends on the speed and load conditions monitored on the vehicle. The (STFT) value changes based on the fuel map weighting cell the engine is operating under in terms of speed and load conditions.
The oxygen sensor is a key element in calculating the fuel trim. If the oxygen sensor indicates a lean mixture, the (STFT) will be increased above the typical value. If the oxygen sensor indicates a rich mixture, the (STFT) will be reduced below the typical value. Under normal operation, fuel trim values will vary between a maximum of 10% and -10%. (STFT) values that exceed this range should be investigated.

P1158 VOLKSWAGEN – Implausible Manifold Absolute Pressure Sensor Signal

P1158 VOLKSWAGEN Possible Causes

  • Faulty manifold absolute pressure sensor
  • Manifold absolute pressure sensor harness is open or shorted
  • Poor electrical connection in the manifold absolute pressure sensor circuit
 

How to Fix Code P1158 VOLKSWAGEN?

Start by checking the “possible causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

 
 

Possible Symptoms

  • Engine light on (or service engine soon warning light)
 

P1158 VOLKSWAGEN Meaning

Implausible signal from the manifold absolute pressure sensor is the generic description for Volkswagen code P1158, but the manufacturer may have a different description for your vehicle model and year. Currently, we do not have further information about the Volkswagen P1158 OBDII code.

P1159 – Air/Fuel Ratio Sensor 1 AFS + Low Voltage Terminal

P1159 Possible Causes

  • Faulty Air/Fuel Ratio Sensor 1
  • Air/Fuel Ratio Sensor 1 harness is open or shorted
  • Poor electrical connection in Air/Fuel Ratio Sensor 1 circuit

How to Fix Code P1159?

Start by checking the “Possible Causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

  • Engine Light On (or Service Engine Soon Warning Light)

P1159 Meaning

The Air/Fuel Ratio (A/F) Sensor 1 is installed in the exhaust system and detects the oxygen content in the exhaust gases. The A/F sensor sends the output voltage to the Engine Control Module (ECM). A heater element for the sensor element is built into the A/F sensor (Sensor 1). It is activated and heats the sensor to stabilize and speed up the detection of oxygen content by controlling the current flowing through the heater. An increase in current stabilizes when the voltage applied to the element electrode reaches a certain range because the amount of oxygen that is routed through the diffusion layer is limited. The current amperage is proportional to the oxygen content in the exhaust gases, so the air/fuel ratio is detected by measuring the current amperage. The ECM compares a set target air/fuel ratio with the detected air/fuel ratio and controls the fuel injection timing.
If the A/F sensor (Sensor 1) voltage is low, the air/fuel ratio is lean and the ECM uses A/F feedback control to issue a Rich command. If the A/F sensor (Sensor 1) voltage is high, the air/fuel ratio is rich and the ECM uses A/F feedback control to issue a Lean command.

P1159 ACURA – Air/Fuel Ratio Sensor 1 AFS + Low Voltage Terminal

P1159 ACURA Possible Causes

  • Faulty Air/Fuel Ratio Sensor 1
  • Air/Fuel Ratio Sensor 1 harness is open or shorted
  • Poor electrical connection in the Air/Fuel Ratio Sensor 1 circuit

How to Fix P1159 ACURA Code?

Start by checking the “Possible Causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

When is the Code Detected?

A malfunction is detected and the code is stored if the heater element is not activated or if the voltage at the Engine Control Module (ECM) terminals is a defined value or less for at least a specified period of time when power is supplied to the A/F sensor heater (Sensor 1).

Possible Symptoms

  • Check Engine Light On (or Service Engine Soon Warning Light)

P1159 ACURA Meaning

The Air/Fuel Ratio (A/F) Sensor 1 is installed in the exhaust system and detects the oxygen concentration in the exhaust gases. The A/F sensor sends the output voltage to the Engine Control Module (ECM). A heating element for the sensor element is built into the A/F sensor (Sensor 1). It is activated and heats the sensor to stabilize and speed up the detection of oxygen concentration by controlling the current flowing through the heater. The current increase stabilizes when the voltage applied to the element electrode reaches a certain range because the amount of oxygen that is transported through the diffusion layer is limited. The current amperage is proportional to the oxygen concentration in the exhaust gases, so the air/fuel ratio is detected by measuring the current amperage. The ECM compares a defined target air/fuel ratio with the detected air/fuel ratio and controls the fuel injection timing.
If the A/F sensor (Sensor 1) voltage is low, the air/fuel ratio is lean and the ECM uses A/F feedback control to issue a Rich command. If the A/F sensor (Sensor 1) voltage is high, the air/fuel ratio is rich and the ECM uses A/F feedback control to issue a Lean command.

P1159 BMW – Fuel Adaptation Additive, Bank 1 High

P1159 BMW Possible Causes

  • Air leaks
  • Faulty mass air flow (MAF) sensor
  • Faulty oxygen sensor, bank 1
  • Low fuel pressure
  • Faulty spark plugs
  • Faulty fuel injectors

How to Fix BMW Code P1159?

Start by checking the “possible causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

  • Check engine light on (or service engine soon warning light)

P1159 BMW Meaning

Short-term fuel trim (STFT) is a value that indicates how the engine control module (ECM) adjusts the factory-programmed fuel map. The fuel map is a lookup table that the controller references. This is used to determine the correct amount of fuel to inject. This amount depends on the speed and load conditions monitored on the vehicle. The (STFT) value changes based on the fuel map weighting cell the engine is operating under in terms of speed and load conditions.
The oxygen sensor is a key element in calculating the fuel trim. If the oxygen sensor indicates a lean mixture, the (STFT) will be increased above the typical value. If the oxygen sensor indicates a rich mixture, the (STFT) will be reduced below the typical value. During normal operation, fuel trim values will vary between a maximum of 10% and -10%. (STFT) values that exceed this range should be investigated.

P1159 BUICK – Cross Counts HO2S, Bank 2 Sensor 2

P1159 BUICK Possible Causes

  • Faulty O2 sensor heater, bank 2 sensor 2
  • O2 sensor heater bank 2 sensor 2 harness is open or shorted
  • O2 sensor heater circuit, bank 2, sensor 2 circuit poor electrical connection
 

How to Fix Code P1159 BUICK?

Start by checking the “possible causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

 
 

Possible Symptoms

  • Engine light on (or service engine soon warning light)
 

P1159 BUICK Meaning

HO2S cross counts, bank 2 sensor 2 is the generic description for code P1159 Buick, but the manufacturer may have a different description for your vehicle model and year. Currently, we do not have more information about the P1159 Buick OBDII code.

P1159 CADILLAC – Cross Counts HO2S, Row 2 Sensor 2

P1159 CADILLAC Possible Causes

  • Faulty O2 sensor heater, bank 2 sensor 2
  • O2 sensor heater bank 2 sensor 2 harness is open or shorted
  • O2 sensor heater circuit, bank 2, sensor 2 circuit poor electrical connection

How to Fix Code P1159 CADILLAC?

Start by checking the “possible causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

  • Engine light on (or service engine soon warning light)

P1159 CADILLAC Meaning

HO2S cross counts, bank 2 sensor 2 is the generic description for code P1159 Cadillac, but the manufacturer may have a different description for your vehicle model and year. Currently, we have no further information about Cadillac OBDII code P1159.

P1159 CHEVROLET – Heated Oxygen Sensor Bank 2 Sensor 2

P1159 CHEVROLET Possible Causes

  • Faulty O2 sensor heater, bank 2 sensor 2
  • O2 sensor heater bank 2 sensor 2 harness is open or shorted
  • O2 sensor heater circuit, bank 2 sensor 2 circuit poor electrical connection
 

How to Fix Code P1159 CHEVROLET?

Start by checking the “possible causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

 
 

Possible Symptoms

  • Engine light on (or service engine soon warning light)
 

P1159 CHEVROLET Meaning

HO2S bank 2 sensor 2 is the generic description for Chevrolet code P1159, but the manufacturer may have a different description for your vehicle model and year. Currently, we have no further information about Chevrolet OBDII code P1159.

P1159 GMC – HO2S Cross Counts, Bank 2 Sensor 2

P1159 GMC Possible Causes

  • Faulty O2 sensor heater, bank 2 sensor 2
  • O2 sensor heater bank 2 sensor 2 harness is open or shorted
  • O2 sensor heater circuit bank 2 sensor 2 circuit poor electrical connection
 

How to Fix Code P1159 GMC?

Start by checking the “possible causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

 
 

Possible Symptoms

  • Engine light on (or service engine soon warning light)
 

P1159 GMC Meaning

HO2S bank 2 sensor 2 is the generic description for code P1159 Gmc, but the manufacturer may have a different description for your vehicle model and year. Currently, we have no further information about OBDII code P1159 Gmc.