When your car throws an OBD2 code, it’s signaling that something isn’t quite right under the hood. Among the myriad of trouble codes, P0107 is a common one that can cause confusion and concern. As an expert at TechcarUSA.com, I’m here to break down the P0107 code, specifically “Manifold Absolute Pressure/Barometric Pressure Circuit Low Input,” helping you understand what it means, what the symptoms are, and how to diagnose and potentially fix the issue.
Understanding the OBD2 Code P0107: Manifold Absolute Pressure Circuit Low Input
The P0107 code is a diagnostic trouble code (DTC) that is generic to OBD-II equipped vehicles, meaning it can appear in a wide range of makes and models. This code specifically points to a problem within the Manifold Absolute Pressure (MAP) sensor circuit.
The MAP sensor plays a crucial role in your engine’s operation. It’s designed to measure the pressure within the intake manifold, which is essentially the vacuum level in your engine. The Engine Control Module (ECM) or Powertrain Control Module (PCM) supplies a 5-volt reference voltage to the MAP sensor. Inside the sensor, a resistor responds to pressure changes, altering the voltage signal sent back to the PCM. This voltage signal typically ranges from about 1 volt (high vacuum/low pressure) to 4.5 volts (low vacuum/high pressure), depending on the engine load. The PCM uses this vital information to calculate fuel delivery and ignition timing.
A P0107 code is triggered when the PCM detects that the MAP sensor signal voltage is abnormally low – specifically, below 0.25 volts. This “low input” condition indicates a potential problem within the MAP sensor circuit that needs attention.
Image: A typical Manifold Absolute Pressure (MAP) sensor, highlighting its role in engine management systems.
Symptoms Associated with OBD2 Code P0107
When the MAP sensor signal is low due to a P0107 error, your vehicle’s performance can be significantly impacted. Because the PCM relies on accurate MAP sensor readings for fuel and ignition control, a fault here can lead to various noticeable symptoms:
- Difficulty Starting: A low MAP sensor signal can severely disrupt the air-fuel mixture, making it hard for the engine to ignite and start.
- Extended Cranking: You might find yourself cranking the engine for a longer period than usual before it finally starts.
- Engine Sputtering or Misfiring: An incorrect air-fuel mixture can cause the engine to run erratically, leading to sputtering or misfires.
- Black Smoke from Exhaust: Too much fuel in the mixture (running rich) due to faulty MAP readings can result in unburnt fuel exiting the exhaust as black smoke.
- Reduced Fuel Economy: Inefficient combustion from an imbalanced air-fuel ratio will often lead to a noticeable drop in fuel mileage.
- Intermittent Stalling: The engine may stall unexpectedly, particularly at idle or low speeds, due to incorrect fuel delivery.
- Illuminated Malfunction Indicator Lamp (MIL): The check engine light will typically illuminate on your dashboard, signaling that a DTC has been set.
Potential Causes of a P0107 Trouble Code
Several factors can lead to a low MAP sensor signal and the P0107 code. Pinpointing the exact cause is crucial for effective repair. Here’s a breakdown of the common culprits:
- Faulty MAP Sensor: The MAP sensor itself could be defective. Internal components can fail, causing it to output an incorrect low voltage signal.
- Signal Circuit Issues: Problems in the signal wire connecting the MAP sensor to the PCM can cause a P0107. This could be an open circuit (broken wire) or a short circuit to ground, both leading to a low voltage reading at the PCM.
- 5-Volt Reference Circuit Problems: The MAP sensor requires a stable 5-volt reference supply from the PCM. An open or short in this reference circuit will disrupt the sensor’s operation and can cause a low signal.
- Ground Circuit Issues: A poor or open ground connection for the MAP sensor can also lead to incorrect readings and trigger the P0107 code.
- PCM Failure (Rare): In less frequent cases, a fault within the PCM itself could be the cause, although this is usually diagnosed after ruling out other possibilities.
- Sensor Interference (Chrysler Vehicles): Notably in Chrysler vehicles, a short circuit in another sensor that shares the 5-volt reference circuit (like a Crankshaft Position Sensor or Vehicle Speed Sensor) can sometimes pull down the voltage and affect the MAP sensor reading, causing a false P0107 code.
Diagnosing and Resolving the P0107 Code
Diagnosing a P0107 code requires a systematic approach. Here’s a step-by-step guide to help you pinpoint and fix the problem:
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Initial Scan Tool Check: Start by using an OBD2 scan tool to confirm the presence of the P0107 code and check for any other related trouble codes. With the key in the ‘on’ position and the engine running, monitor the MAP sensor voltage reading on the scan tool. A reading below 0.5 volts with a P0107 code strongly suggests a low input issue.
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5-Volt Reference Voltage Test: Turn off the engine and disconnect the MAP sensor connector. Use a Digital Volt-Ohm Meter (DVOM) to check for the 5-volt reference voltage at the MAP sensor connector. You should measure approximately 5 volts between the reference voltage pin and ground.
- If No 5V Reference: If there’s no 5-volt reference, check for the reference voltage at the PCM connector. If the 5 volts is present at the PCM but not at the MAP sensor connector, there’s an open circuit in the reference wire between the PCM and the MAP sensor. Repair this open. If there’s no 5-volt reference voltage at the PCM connector itself, investigate the PCM’s power and ground supply and repair or replace the PCM as needed. Note for Chrysler vehicles: If you encounter a missing 5V reference on a Chrysler, suspect a shorted sensor on the same 5V circuit. Disconnect sensors one by one (Crankshaft Position Sensor, Vehicle Speed Sensor, etc.) until the 5V reference returns. The last sensor disconnected is likely the culprit and needs replacement.
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Signal Circuit Test: If the 5-volt reference is present at the MAP sensor connector, use a jumper wire to connect the 5-volt reference pin to the signal pin at the MAP sensor connector (with the sensor still disconnected). Now, check the MAP sensor voltage reading on the scan tool again. It should now read approximately 4.5 to 5 volts.
- If Voltage is Now Correct (4.5-5V): This indicates the MAP sensor is likely faulty and needs to be replaced.
- If Voltage Remains Low: The issue is likely in the signal wire itself – either an open or a short to ground. Inspect the signal wire for damage and repair any wiring issues. Re-check the voltage after repairs.
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Wiggle Test: If wiring appears intact, perform a “wiggle test.” Start the engine and gently wiggle the MAP sensor connector and harness wiring while monitoring the MAP sensor voltage on the scan tool. Also, lightly tap on the MAP sensor itself. Observe if any of these actions cause changes in voltage or engine behavior. This can help identify intermittent connection problems or a sensitive sensor. Repair or replace the connector, wiring, or sensor as needed based on your findings.
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Vacuum Test: With the engine off, use a vacuum pump (or carefully apply vacuum using a hose and your mouth) to draw vacuum on the MAP sensor’s vacuum port. As you apply vacuum, the MAP sensor voltage reading on the scan tool should decrease. With no vacuum applied, the sensor should read around 4.5 volts. If there’s no change in the MAP sensor reading during this test, the sensor is likely faulty and needs replacement.
Related OBD2 Codes to P0107
When diagnosing MAP sensor issues, it’s helpful to be aware of related OBD2 codes:
- P0105: MAP/Barometric Pressure Circuit Malfunction
- P0106: MAP/Barometric Pressure Circuit Range/Performance Problem
- P0108: MAP/Barometric Pressure Circuit High Input
- P0109: MAP/Barometric Pressure Circuit Intermittent
These codes, along with P0107, all relate to the MAP sensor circuit and can sometimes occur together or point to similar underlying issues.
Still Need Help with P0107?
Troubleshooting OBD2 codes can sometimes be complex. If you’re still facing difficulties resolving the P0107 trouble code after following these steps, don’t hesitate to seek further assistance. You can post your question in our FREE car repair forums at techcarusa.com, where our community of experts and enthusiasts can offer guidance and support.
Disclaimer: This information is for informational purposes only and is not intended as professional repair advice. Always consult with a qualified automotive technician for diagnosis and repair. We are not responsible for any actions taken based on this information.
