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DTC codes / Nissan codes / P1129

P1129 · NissanMAP Higher Than Expected

P1129 on Nissan vehicles indicates that the manifold absolute pressure (MAP) sensor signal is higher than the engine control module (ECM) expects for the current operating conditions, meaning the sensor is reporting a lower vacuum or higher pressure than the engine should be producing. The ECM compares the MAP sensor voltage against its internal model of engine load and flags this code when the reading exceeds the calculated threshold for a set period.

SystemPowertrain
Code typeNissan specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • Check engine light illuminated, often with no other noticeable symptoms
  • Rough idle or unstable engine speed, especially when cold
  • Hesitation or stumble during acceleration
  • Poor fuel economy or rich-running condition with black exhaust smoke
  • Elevated idle speed or surging at idle
  • In severe cases, the engine may stall or enter limp mode

Common causes, most likely first

  1. Vacuum leak between the intake manifold and MAP sensor, or a cracked or disconnected vacuum hose
  2. Faulty MAP sensor giving an inaccurate high-pressure signal
  3. Contaminated or clogged MAP sensor sensing element
  4. Wiring issue in the MAP sensor circuit, such as a short to voltage or high resistance in the signal wire
  5. Intake manifold leak or loose intake ducting after the throttle body
  6. Engine mechanical issue such as low compression or incorrect valve timing that reduces manifold vacuum
  7. ECM software or calibration issue, though rare on Nissan vehicles

How to diagnose and fix it

  1. Inspect all vacuum hoses and intake ducting for cracks, loose clamps, or disconnected lines, and repair as needed
  2. Use a scan tool to compare MAP sensor voltage and calculated load against manufacturer specifications at idle and during a snap throttle test
  3. Check the MAP sensor wiring and connector for corrosion, chafing, or a short to voltage, and perform a voltage drop test on the signal circuit
  4. Remove and inspect the MAP sensor for contamination or damage, and clean or replace it if it does not respond correctly to vacuum changes
  5. Perform a vacuum gauge test at the intake manifold to verify actual engine vacuum and rule out mechanical issues
  6. If vacuum and wiring are good, test the MAP sensor with a hand vacuum pump and compare its output to a known-good sensor or manufacturer chart
  7. After repairs, clear the code and perform a drive cycle to confirm the code does not return

What a high MAP reading really means

  • A high MAP signal often indicates a vacuum leak rather than a failed sensor, so technicians who replace the MAP sensor first frequently see the code return.
  • Nissan MAP sensors can become contaminated by oil vapours from the PCV system, causing a skewed high reading that mimics a vacuum leak.
  • A restricted exhaust or incorrect valve timing can reduce manifold vacuum and set P1129 without any sensor or wiring fault.
  • On some Nissan models, a loose or missing oil dipstick or oil filler cap can create a vacuum leak large enough to trigger this code.
  • The ECM may set P1129 in conjunction with P0101 or P0171, so always check for other codes before condemning the MAP sensor.

Can I keep driving with P1129?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration or towing because the engine may run rich and lack power. If the engine idles roughly or stalls, stop driving and have it diagnosed promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Nissan vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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