P1132 – Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 1 (Ford)

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By Reinier (Contact Me)
Last Updated 2022-02-07
Automobile Repair Shop Owner

CodeFault LocationProbable Cause
P1132 P1132 – Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 1 (Ford)
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Manufacturer Specific Definitions for P1132

MakeFault Location
AudiHeated oxygen sensor (HO2S) 1, Bank 1 & 2 - heater control - circuit high
BmwFuel System Error
BuickH02S Circuit Low Variance Bank 2 Sensor 1
CadillacH02S Circuit Low Variance Bank 2 Sensor 1
ChevroletHeated oxygen sensor (H02S) 1, bank 1 signal circuit shorted to heater circuit
CitroenLack Of HO2S Switch - Sensor Indicates Rich
DaewooLiquid Fuel Sol. Fault
DaihatsuAir flow abnormal when Emergency home active
FordLack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 1
GmHO2S Circuit Low Variance Bank 2 Sensor 1
HyundaiLiquid Fuel Solenoid Malfunction
InfinitiSwirl Control Valve Circuit
Land RoverHeated oxygen sensor (H02S), upstream, bank 1 – mixture too rich
LincolnHeated oxygen sensor (H02S) 1, bank 1 -not switching, fuel trim (FT) rich mixture
MahindraShort Circuit Over Load Error For Egr Valve H-Bridge
MazdaHeated oxygen sensor (H02S) 1, bank 1 – rich mixture indicated
Mercedes-BenzHeated oxygen sensor (H02S) control 1 – system too rich
MercuryHeated oxygen sensor (H02S) 1, bank 1 not switching, fuel trim (FT) rich mixture
MiniO2 Sensor Heater Control Circuit Bank 1 Sensor 1
NissanIntake manifold air control solenoid – circuit malfunction
PeugeotLack Of HO2S Switch - Sensor Indicates Rich
PontiacH02S Circuit Low Variance Bank 2 Sensor 1
SaabHeated oxygen sensor (H02S) 1, bank 1 – malfunction
SaturnH02S Circuit Low Variance Bank 2 Sensor 1
SubaruHeated oxygen sensor (H02S) 1 -voltage low
SuzukiHeated oxygen sensor (H02S) 1, bank 1 – heater control – circuit high
VolvoHeated oxygen sensor (H02S) 1, bank 1 – signal high
VolkswagenHeated oxygen sensor (HO2S) heater control - circuit high

What Does Code P1132 Mean?

OBD II fault code P1132 is a manufacturer-specific trouble code that is defined by carmaker Ford as, “Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 1), or sometimes as “Lack of HO2S-11 Switching, HO2S Signal High Input”,  and is set when the PCM (Powertrain Control Module) detects a lack of variation in the upstream oxygen sensor’s signal voltage.

NOTE: In the context of code P1132 as it applies to Ford vehicles-

  • “Bank 1” refers to the bank of cylinders on V-type engines that contains cylinder #1
  • “Upstream oxygen sensor” refers to the oxygen sensor that is located before the catalytic converter
  • Although the wording of the two definitions for code P1132 (as it applies to Ford vehicles) given here differ slightly, both definitions refer to the same issue, i.e., a lack of variation in the upstream oxygen sensor’s signal voltage.

The primary function of oxygen sensors on all Ford vehicles is to measure the concentration of oxygen in the exhaust stream, this concentration being a function of a) the composition of the air/fuel mixture, and b), the efficiency of the combustion process.

In practice, upstream oxygen sensors, i.e., those oxygen sensors that are placed before the catalytic converter, sample “raw” exhaust gas, and the oxygen in the exhaust gas produces an electrical signal that is passed back to the PCM via a dedicated signal circuit. As a practical matter, the PCM supplies the sensor with a 5-volt reference voltage, which voltage changes in direct response, and to a predictable degree, when oxygen comes into contact with the sensing element. Thus, the upstream oxygen sensor “keeps track” of the amount of oxygen in the exhaust stream as the engine speed and load change due to changes in the throttle opening.

In terms of operating principles, the oxygen sensor generates an electrical signal of about 450 millivolts when the air/fuel mixture is stoichiometric, which represents an air/fuel mixture of 14.7 parts of air to one part of fuel. So, assuming that the engine management system is in closed-loop operation*, the PCM will neither add, nor subtract fuel from the mixture, since at a stoichiometric level, the engine is performing at its peak, and exhaust emissions are minimized.

*Closed loop operation happens when the PCM reacts to input data from the oxygen sensor. In open-loop operation, the PCM reverts to a default fueling strategy, because input data from the oxygen sensor is not available. On all modern vehicles, closed-loop operation only becomes possible when the oxygen sensor is fully functional, and the sensor’s sensing element is heated to a specified temperature.

However, during throttle inputs, the air to fuel ratio changes to a mixture that contains more than one part of fuel to 14.7 parts of air. This is known as a “rich” mixture, and the oxygen sensor reacts to this change by generating a signal voltage that can range from about 450 millivolts to as high as about 950 millivolts, which the PCM interprets as a rich mixture. To correct this, the PCM will reduce the time the injectors have to inject fuel* to subtract fuel from the mixture to return the air/fuel mixture to stoichiometric value.

*This time is more properly known as the injectors’ “pulse width” or “duty cycle”. The addition or subtraction of fuel from the air/fuel mixture is known as short-term positive or negative fuel trims, respectively.

In terms of practicalities, however, these types of corrections to the air/fuel mixture are typically large and can take significant amounts of time to complete. So to avoid the need to make several large changes to the air/fuel mixtures, the PCM deliberately switches the oxygen sensor to read lean and rich mixtures alternately several times per second, regardless of the actual composition of the air/fuel mixture at any given moment.

The practical advantage of this strategy is that the PCM can make several small changes to the air/fuel mixture in less time than it takes to make one large adjustment. Moreover, by making many small changes to the air/fuel mixture in rapid succession, the PCM can maintain the air/fuel mixture in a much narrower range (on either side of stoichiometric) much more effectively than is possible to do with a few large adjustments that take a long time to complete and verify.

Thus, in a fully functional fuel delivery system, the PCM expects to see rapidly changing or fluctuating signal voltages from the upstream sensor as it responds to the lean/rich switching strategy it imposes on the sensor. Therefore, when a defect, failure, or malfunction occurs that-

  • prevents the oxygen sensor from alternately switching to read lean or rich mixtures
  • prevents the PCM from commanding the switch between reading lean and rich mixtures
  • that causes the oxygen sensor to become “stuck” in the sense that it only reports a rich mixture

– the PCM will recognize that it cannot control the air/fuel mixture effectively, and will set code P1132 and illuminate a warning light as a result. Note that this condition will typically not result in the initiation of a limp mode, but the PCM will revert to a default fuelling strategy that may limit the engine’s power output in some cases.

Where is the P1132 sensor located?

This image shows the location (orange arrow) of the upstream oxygen sensor on a 2014 Ford Focus application. The green arrow indicates the direction of flow through the exhaust system.

Note, though, that many Ford vehicles accommodate multiple sensors on and in the exhaust system, and testing, removing, or replacing the wrong sensor is an easy mistake to make. Therefore, we strongly recommend that you consult reliable service information for the affected vehicle to locate and identify the upstream oxygen sensor correctly because the upstream oxygen sensor is not always the sensor that is located closest to the engine- as shown here.

What are the common causes of code P1132?

The most common causes of code P1132 on Ford vehicles are similar across all models, and could include one or more of the following-

  • Damaged, shorted, disconnected, or corroded wiring and/or connectors anywhere between the upstream oxygen sensor and the PCM
  • Damaged or defective upstream oxygen sensor
  • The use of substandard aftermarket oxygen sensors
  • Leaks in the exhaust system that contaminate the air under the vehicle; oxygen sensors use ambient air as a reference to calculate the level of oxygen in the exhaust stream
  • Restrictions in the exhaust system that prevent the free flow of exhaust gas through the exhaust system
  • One or more damaged or defective fuel injectors that inject more fuel into the cylinders than the PCM can compensate for
  • Excessive oil consumption, which a), may reduce the upstream oxygen sensors’ sensitivity, and/or b), coats the oxygen sensor’s sensing element with partially combusted oil. Note that both conditions could result in the upstream oxygen sensor reporting an overly rich air/fuel mixture
  • Excessive fuel pressure, but note that this condition will always be indicated by a dedicated fuel pressure-related trouble code
  • Failed or failing PCM, but note that since this is a rare event, the fault must be sought elsewhere before any control module is reprogrammed or replaced

What are the symptoms of code P1132?

Common symptoms of code P1132 on Ford vehicles are largely similar across all models and could include one or more of the following, but note that in some cases, there may be no discernable symptoms present apart from a stored trouble code and a warning light-

  • Stored trouble code and an illuminated warning light that may or may not flash
  • Depending on the nature of the problem, multiple additional codes could be present along with P1132, some of which may refer to fuel pressure, exhaust backpressure, or misfires
  • In some cases, the engine’s power output may be restricted
  • Depending on the nature of the problem, fuel consumption may increase
  • The exhaust gas may have a strong odor of unburned fuel
  • In most instances of this code, the engine may run roughly at some engine speeds, or the idling quality may be poor
  • Throttle inputs may produce sluggish acceleration
  • Depending on the nature of the problem, catalytic converter(s) could suffer fatal damage if the problem is not found and corrected promptly
  • Some readiness monitors may not initiate or may not run to completion
  • The vehicle will not pass an emissions test

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