P1122 – Electric Throttle Control Performance Problem (INFINITI, NISSAN)

By Reinier (Contact Me)
Last Updated 2019-09-19
Automobile Repair Shop Owner

Manufacturer Specific Definitions for P1122

Table of Contents

1. What Does Code P1122 Mean?
2. Where is the P1122 sensor located?
3. What are the common causes of code P1122?
4. What are the symptoms of code P1122?
5. Get Help with P1122

What Does Code P1122 Mean?

OBD II fault code P1122 is a manufacturer specific code that is defined by car maker Nissan as “Electric Throttle Control Performance Problem”, and is set when the PCM (Powertrain Control Module) detects an abnormally high or low signal voltage from the electronically controlled throttle actuator. Note that in this context, “abnormal” refers to actual signal voltages that do not agree with desired and/or expected voltages, given the current operating conditions.

In practice, electronically controlled throttle actuators are used to replace mechanical linkages such as control cables to control the opening and closing of the throttle. Known as drive-by-wire systems, these systems use dedicated throttle pedal position sensors to monitor the movement of the throttle pedal. In terms of their operation, typical throttle pedal position sensors are simple potentiometers that are fed with a 5-volt reference current by the PCM. When the throttle pedal is at rest, i.e., the closed position, the sensor’s internal resistance is very low, and almost all of the reference voltage is therefore passed back to the PCM, which interprets the high voltage as evidence that the throttle is in the closed position.

When the throttle pedal is depressed, the resistance of the throttle position sensor increases in direct proportion to the amount of movement of the pedal. As a practical matter, this means that the further the throttle position is depressed, the more the sensor’s resistance increases, which in turn, progressively reduces the voltage of the current that is fed back to the PCM, which interprets the lowest allowable voltage as evidence that the throttle plate is in the fully open position.

In terms of actual throttle control, the PCM uses the changing signal voltages it receives from the throttle pedal position sensor to calculate appropriate throttle openings, which are accomplished by signals the PCM sends to a stepper motor that is incorporated into the throttle body. Thus, a percentage of the throttle pedal position sensors’ travel, say 50%, should produce a signal voltage that can be converted into a throttle opening of 50%, and in a fully functional system, this would indeed happen, and this would be confirmed by a dedicated sensor that monitors the actual (as opposed to the desired) position of the throttle plate.

However, due to the harsh operation conditions electronic throttle system components are subjected to, many conditions can develop that prevent a direct correlation between the throttle pedal, and the actual opening of the throttle plate. In these cases, it can happen that the PCM expects to “see” a throttle opening of say, 50% (based on inputs from the throttle pedal position sensor), while the throttle position sensor is reporting an actual opening of say, only 35%.

When this happens, the PCM will recognize that it cannot control the throttle accurately or effectively, and it will set code P1122 and illuminate warning light as a result. Note that in some cases, the PCM may also initiate, and maintain a fail-safe or limp mode as a safety precaution until the fault is corrected, and the required adaptations and/or relearning procedures have been completed successfully.

Where is the P1122 sensor located?

The image above shows an example of an electronic throttle control assembly, such as might be found on many Nissan Maxima models. Note the red arrow; in this case, the arrow indicates the position of the integrated DC stepper motor that controls the movement of the throttle plate via a set of drive gears that is contained in the black plastic part of the assembly, which also contains the electrical connector.

Note though that the actual appearance of electronic throttle bodies vary between Nissan applications, but in all cases, the throttle body is located in the large diameter ducting between the air filter box and the intake manifold. In most cases, the throttle body bolts directly onto the intake manifold, which makes it easy to locate; simply look for an electrical connector on a part that bolts onto the intake manifold.

What are the common causes of code P1122?

Common causes of code P1122 on Nissan applications are many and varied, but could include one or more of the following-

• Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors anywhere in the throttle body’s control signal circuits
• Defective/damaged/worn throttle position sensor
• Defective or damaged throttle pedal position sensor
• Defective or worn throttle body
• Defective or worn drive gears in the throttle body
• Defective or damaged stepper motor in the throttle body
• Excessive carbon build-up that prevents free movement of the throttle plate
• Use of some aftermarket throttle bodies
• Failure to successfully perform required adaptations/integrations/or relearning procedures after a throttle body replacement
• Failed or failing PCM, but note that since is a rare event, the fault must be sought elsewhere before any control module is replaced

What are the symptoms of code P1122?

Common symptoms of code P1122 on Nissan applications can be many and varied, but could include one or more of the following-

• Stored trouble code, and illuminated warning light
• In many cases, multiple additional codes may be present along with P1122, and most notably, codes that relate to mis-correlations between the throttle pedal position sensor and the throttle position sensor
• Engine may be difficult to start, or the engine may not start at all
• Idling speed may fluctuate, or the idling may be rough- usually because the idling speed is too low
• Idling speed may exceed the specified or recommended speed
• Engine may stall unexpectedly- especially at low engine speeds or when coming to a stop
• Gear shifts may be harsh, erratic, or unpredictable
• Engine may not respond to throttle inputs as expected, or may not respond to throttle inputs at all
• Severe loss of power loss may be present
• If a fail-safe or limp mode is initiated and enforced, nether the throttle nor the transmission may respond to manual inputs

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