P0108 on 2017-2024 Mazda CX-5: MAP Sensor Circuit High Causes and Fixes

What's Unique About the 2017-2024 Mazda CX-5

On the Mazda CX-5's Skyactiv-G engines, the MAP sensor is a standalone, easily accessible component mounted directly on the intake manifold. Unlike some vehicles that integrate it with other sensors, its individual placement simplifies diagnosis and replacement. While the code itself is generic, the most common failure point on this platform is the sensor itself rather than more complex issues like wiring harnesses or PCM faults. The PCM has a specific fail-safe strategy for this code, where it will estimate the MAP value using the MAF sensor and engine speed, but may restrict engine speed as a precaution.

Symptoms You May Notice

• Check Engine Light is on
• Rough or unstable idle
• Poor acceleration and engine hesitation
• Increased fuel consumption
• Black smoke from the exhaust
• Engine may stall, especially at idle
• Hard starting or no-start condition

Most Likely Causes

1. Faulty Manifold Absolute Pressure (MAP) Sensor 🔴 High Probability → Shop Manifold Absolute Pressure Sensor Sensors can fail over time due to heat cycles and internal electronic degradation. This is the most frequently reported fix across Mazda forums and repair databases for a P0108 code.
   How to confirm: With the Key On, Engine Off (KOEO), use a scan tool to check if the MAP sensor voltage reading is stuck high, near 5V. It should read around 4.0-4.5V and match the Barometric Pressure (BARO) reading. When the engine is started, the voltage at idle should drop to around 1.2-1.5V. If the voltage remains high, the sensor has failed.
   Typical fix: Replace the MAP sensor. It is typically held in by a single bolt or screw and has one electrical connector, making it a 15-minute job.
   Est. part cost: $40-$160
2. MAP Sensor Circuit Wiring or Connector Issue 🟡 Medium Probability → Shop Manifold Absolute Pressure Sensor
   How to confirm: Visually inspect the wiring harness and connector for damage, corrosion, or loose pins. Use a multimeter to check for a 5-volt reference signal and a good ground at the connector. Check for a short to power on the signal wire, which would cause a constant high voltage reading.
   Typical fix: Repair the damaged section of wiring or clean/replace the connector pigtail.
   Est. part cost: $5-$50
3. Clogged Catalytic Converter ⚪ Low Probability
   How to confirm: A severely restricted exhaust will cause a loss of power, especially at high RPMs, and can artificially raise pressure in the intake manifold. A technician can perform an exhaust backpressure test to confirm a blockage. This is usually accompanied by other codes like P0420.
   Typical fix: Replace the clogged catalytic converter.
   Est. part cost: $800-$2000+

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is very rare. All other possibilities, especially the sensor and its wiring, should be exhaustively ruled out before considering the PCM as the cause.

Diagnosis Steps

1. Connect an OBD-II scanner and confirm P0108 is present. Note any other codes, but P0108 is often a standalone code for this issue.
2. View live data with the scanner. With the Key On, Engine Off (KOEO), compare the MAP sensor voltage to the BARO reading. They should be nearly identical (around 4.0-4.5V at sea level). A MAP reading stuck at or near 5V points to a bad sensor or a short in the signal wire.
3. Start the engine. At idle, the MAP sensor voltage should drop significantly to 1.2-1.5 volts due to engine vacuum. If the reading does not change or stays high, the sensor is likely faulty or its vacuum port is blocked.
4. Turn off the engine. Visually inspect the MAP sensor's electrical connector and wiring for any signs of damage, corrosion, or loose connections.
5. If wiring looks good, disconnect the sensor. With the key on, use a multimeter to verify you have a 5V reference wire and a good ground wire at the connector. Check the signal wire for any voltage; it should be near 0V with the sensor disconnected. If voltage is present, there is a short to power in the harness.
6. If the sensor and wiring test good, consider a possible severe restriction in the exhaust system (e.g., a clogged catalytic converter) that could cause abnormally high manifold pressure.

Parts You'll Likely Need

• Manifold Absolute Pressure (MAP) Sensor (OEM #PE02-18-211) — This is the most common failure component for a P0108 code. It directly measures the manifold pressure that the code references. This part number is specific to the non-turbo Skyactiv-G engines.
  Trusted brands: Mazda (OEM), Denso, Bosch, Standard Motor Products, Goss
  OEM price range: $90-$125
  Aftermarket price range: $40-$80

Platform-Specific Known Issues

• While not directly causing P0108, owners should be aware that the Skyactiv-G Direct Injection engines can be prone to carbon buildup on the intake valves over time. While Mazda's design aims to minimize this, it can still occur, especially with extensive short-trip driving. Severe buildup could theoretically affect manifold pressure, but it's unlikely to be the primary cause of a P0108 code.

Mechanic-Grade Diagnostic Values

• PCM Fault Trigger Threshold — expected: Input voltage at PCM terminal 1BW should be below 4.89V.. Failure: If voltage is > 4.89 V for 5 seconds, the PCM logs P0108.
• MAP Sensor Voltage (MAP_V PID) — expected: Approx. 4.08 V (Key On, Engine Off at sea level). Failure: Voltage stuck near 5V or significantly different from expected.
• MAP Sensor Voltage at Idle (MAP_V PID) — expected: Approx. 1.25 V (after warm-up). Failure: Voltage does not drop from KOEO reading or stays high.
• Sensor Connector - Reference Voltage — expected: Approx. 5V at the reference wire terminal with key on.. Failure: Significantly less than 5V indicates a wiring or PCM issue.

Scan Tool Commands That Help

• Mazda M-MDS / FORScan: PID/DATA Monitor for 'MAP' and 'MAP_V' — This is the primary function to observe live voltage and pressure readings from the sensor at KOEO and idle to determine if it's responding correctly.

Wiring & Ground Locations

• PCM — Located under the battery tray in the engine compartment.. The PCM is the endpoint for the MAP sensor wiring. If the sensor and its connector are good, testing for a short or open circuit must be done at the PCM connector pins.
• MAP Sensor Signal Wire — Runs from MAP sensor/IAT sensor No.2 terminal D to PCM terminal 1BW.. A short to power on this specific wire is a likely cause for P0108 if the sensor itself is not faulty.
• MAP Sensor Ground Wire — Runs from MAP sensor/IAT sensor No.2 terminal C to PCM terminal 1BO.. An open circuit on this ground wire can cause the sensor's signal voltage to float high, triggering a P0108 code.
• MAP Sensor 5V Reference Wire — Runs from MAP sensor/IAT sensor No.2 terminal A to PCM terminal 1BX.. An open circuit on this wire would cause the sensor to stop functioning, likely triggering a different code (P0107), but a short to a higher voltage source could cause P0108.
• Engine Ground Points — Key grounds are located on the passenger side motor mount, on top of and on the front of the transmission case, and from the driver-side fender area to the negative battery terminal.. While a bad ground is more likely to cause a P0107 (low voltage), a poor PCM ground can cause a variety of unpredictable sensor reading issues, including a floating high signal.

Real Owner Repair Stories

• YouTube user 'The Car Care Nut' (Mazda 6 2.2 Skyactiv (similar MAP sensor diagnostics)) — Check engine light, MAP sensor code.
  ❌ Tried (didn't work) The owner purchased a new aftermarket MAP sensor.
  ✅ What actually fixed it The new aftermarket MAP sensor was faulty out of the box, providing incorrect live data readings (36.98 PSI vs. a desired 16.35 PSI at KOEO). Swapping in a known-good OEM sensor from a friend's CX-5 showed correct readings (14.5 PSI). The final fix was to use a genuine, working sensor.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Cracked Cylinder Head (2.5L Turbo & some NA) 🔴 High — Primarily reported on 2.5T engines, but also some non-turbo models. Can occur outside of warranty. TSB 01-002/23 addresses the issue for some 2019-2020 models by noting coolant leaks near the exhaust manifold. (Ref: TSB 01-002/23)
• Infotainment 'Ghost Touch' 🟡 Low — Common issue on 2017-2020 models where the screen registers phantom touches, causing random inputs. Often resolved by disconnecting the touchscreen ribbon cable, as most users rely on the commander knob. (Ref: SSPB6 (Warranty extension for Mazda 3, but CX-5 has the same issue))
• Rocker Arm Failure (Cylinder Deactivation Engines) 🔴 High — Affects 2018-2019 models with cylinder deactivation. A software issue could cause a rocker arm to dislodge, potentially leading to engine stall and failure. (Ref: Recall 3719F / NHTSA #19V-497)
• Intake Valve Carbon Buildup 🟠 Medium — A known characteristic of all Skyactiv-G direct injection engines. Oil vapors from the PCV system can bake onto the intake valves over time, as they are not washed by fuel. Can cause performance loss at higher mileage. Mazda's design mitigates it, but it's not eliminated.
• Flickering LED Daytime Running Lights (DRL) 🟡 Low — Commonly reported on 2016-2017 models. The gasket around the headlight assembly can fail, allowing moisture in and causing the DRL to flicker or fail completely. Requires replacement of the headlight assembly.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used OEM sensor from a low-mileage donor vehicle can be a cost-effective and reliable alternative to a new aftermarket part. Since the failure mode is typically electronic and not wear-based, a working used part is likely to remain working.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Ensure the donor vehicle was not in a front-end collision.
• Inspect the connector pins for any signs of corrosion or damage.
• Check that the O-ring is present and not brittle or cracked.

Aftermarket brands forum-validated for this vehicle:

• Denso
• Bosch

Brands owners have reported issues with on this vehicle:

• Unbranded, 'white-box' parts from online marketplaces should be avoided. As seen in a documented repair, a brand-new aftermarket sensor can be faulty out of the box, leading to significant diagnostic confusion.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0420 — Often accompanies P0108 if the root cause is a severely restricted exhaust or clogged catalytic converter.
• P0098 — Intake Air Temperature Sensor 2 Circuit High; observed appearing alongside P0108 in owner reports involving circuit/electrical issues.
• P0118 — Engine Coolant Temp Sensor 1 Circuit High; noted in owner reports as a companion code during electrical system malfunctions.
• P0193 — Fuel Rail Pressure Sensor A Circuit High; can appear with P0108 when multiple sensor circuits experience high voltage or grounding issues.
• P0123 — Throttle/Pedal Position Sensor/Switch A Circuit High; identified in owner reports as a related code during broad electronic failures affecting the MAP sensor.

Frequently Asked Questions