What Does P1107 Mean?
P1107 indicates either a dual alternator lower circuit malfunction or a MAP sensor circuit producing intermittent low voltage. For the MAP interpretation, the signal drops below the expected range sporadically, suggesting either a loose connection or a sensor that momentarily loses power. This causes momentary lean conditions and potential engine hesitation. For the alternator interpretation, the lower alternator control circuit has an electrical fault.
Common Causes
30%
Intermittent open circuit in MAP sensor signal wire
25%
MAP sensor connector with loose or corroded ground pin
18%
Dual alternator lower unit control circuit open or high resistance (if equipped)
17%
MAP sensor failing intermittently under temperature changes
10%
ECM ground issue affecting MAP sensor reference circuit
Diagnostic Steps
1
Step 1: Monitor MAP sensor voltage at idle. It should read a steady 1.0–2.0V. Any dropouts to 0V or near 0V indicate an intermittent open in the circuit.
2
Step 2: Perform a wiggle test on the MAP sensor connector and wiring harness while monitoring live data. Note any voltage drops that coincide with movement.
3
Step 3: Check the 5V reference voltage at the MAP sensor connector with the sensor unplugged. If the reference is unstable, the issue may be in the shared reference circuit or ECM.
4
Step 4: Inspect the sensor ground circuit for high resistance using a voltage drop test. More than 0.1V drop on the ground wire indicates a poor ground connection.
5
Step 5: For dual alternator vehicles, test the lower alternator control circuit continuity and connector integrity. Check for corroded connections at the alternator and PCM.
Estimated Repair Cost
$50 - $350
Parts + labor, varies by vehicle and location
P1107 indicates either a dual alternator lower circuit malfunction or a MAP sensor circuit producing intermittent low voltage. For the MAP interpretation, the signal drops below the expected range sporadically, suggesting either a loose connection or a sensor that momentarily loses power. This cause...
The most common cause of P1107 (Dual Alternator Lower Circuit Malfunction/ Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent Low Voltage) is: Intermittent open circuit in MAP sensor signal wire
Typical repair costs for P1107 range from $50 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Intermittent low MAP voltage readings can cause lean misfires and hesitation during acceleration. While not immediately dangerous, sustained lean conditions can damage catalytic converters and cause overheating.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1107 to identify the root cause.
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Powertrain
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Engine Management / Charging System
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