P1120
NissanNissan DTC P1120 indicates an issue with the Accelerator Pedal Position (APP) Sensor circuit, specifically when the Engine Control Module (ECM) detects that the sensor's voltage signal is outside its specified operating range. This means the engine's computer isn't getting a clear understanding of how much the driver is pressing the accelerator.
Medium SeverityThis code means your vehicle's computer, the Engine Control Module (ECM), isn't getting a proper signal from the Accelerator Pedal Position (APP) Sensor. Essentially, the car can't accurately tell how much you're pressing the gas pedal, which directly affects how the electronic throttle body responds.
⚠️ Before You Begin (Safety First)
Before attempting any electrical work, always disconnect the negative battery terminal to prevent accidental shorts or damage to the vehicle's electrical system. Remember, we want to keep you and your vehicle safe! Be cautious around hot engine components and moving parts.
Common Symptoms
- Check Engine Light (CEL) illuminated
- Reduced engine power or 'limp mode' activation
- Hesitation or surging during acceleration
- Unresponsive accelerator pedal
- Vehicle may not accelerate above a certain speed
- Rough idling or stalling
Common Causes
- A faulty Accelerator Pedal Position (APP) sensor itself, meaning the internal components are no longer sending a correct signal
- Corroded, frayed, or damaged wiring in the APP sensor circuit, preventing a clean signal from reaching the ECM
- Loose or poor electrical connections at the APP sensor or at the Engine Control Module (ECM), which is like having a bad phone connection
- A short circuit or an open circuit within the APP sensor wiring harness, stopping the signal entirely or creating an incorrect one
- Less commonly, an internal issue with the Engine Control Module (ECM) itself, which is the brains of the operation
Frequently reported on: Nissan Altima (2002-2006), Nissan Maxima (2000-2003), Nissan Sentra (2000-2006), Nissan Pathfinder (2001-2004), Nissan Xterra (2000-2004)
Diagnostic Steps
- Connect an OBD-II scanner to your vehicle to confirm the P1120 code is present and check for any other related codes that might give you more clues. This is your first step in understanding the whole picture.
- Visually inspect the entire wiring harness leading to the Accelerator Pedal Position (APP) sensor for any signs of damage, fraying, or corrosion. Remember, even a small nick in a wire can cause big problems with electrical signals.
- Carefully check the electrical connector at the APP sensor itself for cleanliness, any bent or pushed-out pins, or a loose fit. Sometimes, it's just a poor connection that's throwing everything off.
- Using a multimeter, you'll want to carefully back-probe the APP sensor connector with the ignition on (Key On, Engine Off - KOEO). Test for proper reference voltage (which is typically 5V) and a good ground. These are essential for the sensor to work.
- If your reference voltage and ground are good, then it's time to test the signal wire voltage from the APP sensor. While slowly depressing the accelerator pedal, you should see a smooth, consistent voltage increase and decrease, not erratic jumps or sudden drops. This tells you if the sensor is accurately reporting pedal movement.
- If the sensor voltage is erratic, inconsistent, or completely absent during your tests, and you've confirmed all connections are good, try cleaning the connector with electrical contact cleaner. If the issue persists, then it's highly likely you're looking at a faulty APP sensor that needs to be replaced.
- After you've completed any repairs, clear the code with your OBD-II scanner. Then, take your vehicle for a thorough test drive to ensure the issue is resolved and, more importantly, that the code does not return. This final step is crucial to verify your hard work!
👨🔧 When to Call a Professional
Alright, if you've checked all the wiring and connectors thoroughly and the issue still persists, or if you're uncomfortable using a multimeter to accurately test sensor voltage and signal integrity, it's definitely time to consult a professional technician. They have specialized diagnostic tools and the experience to pinpoint those tricky intermittent electrical faults that can sometimes be hard to find.
Commonly Asked Questions
What exactly does the Accelerator Pedal Position (APP) Sensor do?
The APP sensor is what tells your car's computer how much you're pressing the gas pedal. Think of it as the electronic link between your foot and the engine's throttle. It sends a voltage signal to the Engine Control Module (ECM), which then commands the electronic throttle body to open or close, letting more or less air into the engine. Without it, the computer doesn't know what you want the engine to do!
Can I drive my Nissan if it has a P1120 code?
While you might be able to drive it, it's generally not recommended. A P1120 code often puts the vehicle into 'limp mode,' which severely limits engine power and speed to prevent further damage. This can be very dangerous, especially if you need to accelerate quickly to merge into traffic or avoid a hazard, so it's always best to address it promptly.
Is the Accelerator Pedal Position Sensor the same as the Throttle Position Sensor?
That's a really good question that often confuses people! While they both measure 'position,' they're usually separate components in modern drive-by-wire systems. The APP sensor measures your foot's input at the pedal, telling the computer what you intend. The Throttle Position Sensor (TPS) measures the actual opening of the throttle blade itself. The APP sensor sends a signal to the ECM, which then sends a command to the throttle body (which contains the TPS) to open to the desired amount. So, they work together, but they're distinct!
How can I tell if the APP sensor is definitely bad or if it's a wiring issue?
The key here is systematic testing with a multimeter, as we discussed in the DIY steps. You'll want to check for proper power and ground at the sensor connector. If those are good, then you test the signal wire while slowly pressing the pedal. If the signal voltage doesn't change smoothly or is completely absent, and all connections are solid, that points more strongly to a faulty sensor. But remember, a break in the signal wire itself could also cause similar symptoms, so a thorough visual inspection and wiggle test are crucial!
Do I need to recalibrate anything after replacing the APP sensor?
For most Nissan vehicles with electronic throttles, yes, after replacing the APP sensor, you'll typically need to perform an idle air volume learning procedure and sometimes a throttle valve closed position learning. These steps help the ECM 'learn' the new sensor's range and ensure the throttle body operates smoothly and correctly. Your service manual or a professional-grade scan tool will have the specific steps you need to follow for your particular model year.