P1157 (Volkswagen, Audi, Skoda, Seat) Manifold absolute pressure (MAP) sensor - supply voltage
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P1157 – OBD-II Trouble Code Technical Description
Trouble code P1156 indicates a problem with the supply voltage of the manifold absolute pressure (MAP) sensor in Volkswagen, Audi, Skoda, Seat vehicles.
What does the fault code mean P1157?
Trouble code P1157 indicates a problem with the manifold absolute pressure (MAP) sensor power circuit. This sensor is responsible for measuring the absolute air pressure in the intake manifold and transmitting the corresponding data to the engine control module (ECM). The supply voltage for this sensor is outside the expected range, indicating a potential problem with its operation or with the electrical circuit that powers it.
Possible reasons
Some possible reasons for the P1157 trouble code:
- MAP sensor malfunction: The MAP sensor itself may be damaged, malfunctioning, or have incorrect readings due to physical wear, corrosion, an open circuit, or other reasons.
- Electrical circuit problems: Faults in the wires, connectors, or relays that supply power to the MAP sensor can result in an incorrect supply voltage or a short to ground, causing a P1157 code.
- Problems with the engine control module (ECM): Faults in the engine control module, which receives data from the MAP sensor and regulates its operation, can also cause the P1157 code.
- Problems with the vacuum system: Leaks or problems in the vacuum system, which is used by the MAP sensor to measure pressure, can cause incorrect readings and an error.
- Problems with the intake system: A clogged or damaged intake system, including a clogged air filter or oil filled intake manifold, can also affect MAP sensor performance and cause P1157.
These causes usually require additional diagnostics to accurately identify and correct the problem.
What are the symptoms of a fault code? P1157?
With DTC P1157, you may experience the following symptoms:
- Loss of power: An inoperative or malfunctioning manifold absolute pressure (MAP) sensor can cause loss of engine power. This can manifest itself in a slower response to the gas pedal and worse acceleration dynamics.
- Unstable engine performance: Incorrect MAP sensor readings may cause engine instability. This can manifest itself in rough idling, a rattling idle, or even random misfires.
- Increased fuel consumption: Improper operation of the MAP sensor can result in an incorrect fuel/air mixture, which in turn can result in increased fuel consumption.
- Increased emissions of harmful substances: If the fuel/air mixture becomes rich (too much fuel), it can cause increased emissions of harmful substances such as hydrocarbons and nitrogen oxides.
- Engine management system errors (Check Engine): When the P1157 code appears, it is usually accompanied by the Check Engine Light turning on on your vehicle's dashboard.
How to diagnose a fault code P1157?
The following steps are recommended to diagnose DTC P1157:
- Checking the error code: Using a scan tool, read the P1157 code from the Engine Control Module (ECM) and record it for later analysis.
- Visual inspection of the MAP sensor and its connections: Inspect the manifold absolute pressure (MAP) sensor and its electrical connections for visible damage, corrosion, or poor connections. Make sure the connectors are securely connected.
- Measuring MAP Sensor Supply Voltage: Using a multimeter, measure the supply voltage at the corresponding pins of the MAP sensor. Make sure the voltage meets the vehicle manufacturer's specifications.
- MAP Sensor Circuit Resistance Test: Measure the resistance of the MAP sensor circuit to ensure it is within the specified range. Abnormalities may indicate problems in the circuit or the sensor itself.
- ECM diagnostics: If necessary, perform additional diagnostics on the engine control module (ECM) to rule out possible engine malfunctions.
- Vacuum system testing: Check vacuum hoses and valves for leaks or damage as this may affect MAP sensor performance.
- Carrying out diagnostic tests: Use specialized hardware and software to perform additional diagnostic tests, such as real-time testing or standby diagnostics.
To successfully diagnose a P1157 code problem, it is important to consider all possible sources of problems and follow professional guidelines and vehicle manufacturer recommendations.
Diagnostic errors
When diagnosing DTC P1157, the following errors may occur:
- Skipping a visual inspection: Some technicians may skip visual inspection of the MAP sensor and its connections, which may result in missing obvious problems such as damage or corrosion.
- Insufficient checking of electrical connections: Checking only the external connections without checking for good connections and condition of the wires may result in missing electrical problems.
- Ignoring manufacturer specifications: Failure to follow manufacturer specifications for MAP sensor supply voltage or resistance may result in incorrect diagnosis.
- Errors in interpreting scanner data: Misinterpretation of data received from the diagnostic scanner may lead to misdiagnosis and misidentification of the problem.
- Misdiagnosis of other components: Sometimes technicians may focus only on the MAP sensor while ignoring other potential causes, such as problems with the engine control module (ECM), vacuum system, or intake system.
- Incorrect problem fix: If the problem of P1157 has not been correctly identified, its resolution may be incomplete or ineffective, which may result in the error reoccurring.
How serious is the fault code? P1157?
Trouble code P1157 is not critical to driving safety, but it does indicate problems with the engine management system that can result in poor performance, increased fuel consumption, and increased emissions. An improper fuel/air mixture caused by a faulty manifold absolute pressure (MAP) sensor can result in loss of engine power and rough running. Therefore, it is recommended that you contact a professional to diagnose and fix the problem as soon as possible to avoid additional damage and deterioration in vehicle performance.
What repair will help eliminate the code? P1157?
Resolving trouble code P1157 typically requires the following steps:
- Manifold Absolute Pressure (MAP) Sensor Replacement: If the MAP sensor is truly faulty or its signal is not being properly transmitted to the Engine Control Module (ECM), then replacing the sensor should correct the problem.
- Electrical circuit check: If the problem is related to the electrical circuit, you need to check the wires and connectors for damage, corrosion or improper contact. If necessary, repair or replace damaged components.
- Engine Control Module (ECM) Diagnosis: In rare cases, the problem may be due to a malfunction of the engine control module itself. If other causes have been ruled out, it may be necessary to further diagnose the ECM and, if necessary, replace it.
- Checking the vacuum system: Leaks in the vacuum system can cause the MAP sensor to read incorrectly. Check vacuum hoses and valves for leaks and replace or repair them if necessary.
- Engine Control Module (ECM) Firmware: Sometimes updating the engine control module software can help resolve trouble codes including P1157.
After completing these steps, it is recommended to test the system and clear the fault code using a diagnostic scanner. If the problem persists, further diagnosis or consultation with professionals may be needed.
