P1107

Code

Other P — Powertrain

Dual Alternator Lower Circuit Malfunction/ Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent Low Voltage

Brand: Other

Type: P — Powertrain

Views: UK: 55 EN: 62 RU: 59

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged or corroded wiring or connector for MAP sensor or alternator control/low circuit
Poor ground or reference (5V) supply to MAP sensor or shared grounding/packaging issues
Weak battery or intermittent charging from alternator (regulator or field circuit problem)
Failing MAP sensor or alternator voltage regulator/module
Blown fuse or fusible link in MAP reference or alternator control circuit
Intermittent PCM or ECU input driver failure

Symptoms

Check Engine Light with P1107 present
Erratic MAP sensor voltage readings or low voltage on scan tool (intermittent)
Poor idle, stalling, hesitation, or reduced engine performance
Battery/charging system warnings, low charge voltage, or fluctuating dash voltmeter
Possible hard starting or reduced electrical charging

What to check

Read and record freeze‑frame and related codes; check pending and history counts
Check battery resting voltage and charging voltage with engine running
Scan live MAP sensor voltage and MAP kPa readings while key on and during engine operation
Verify 5V reference and signal ground at MAP sensor connector with key on
Inspect wiring and connectors for damage, corrosion, heat, or water intrusion at MAP sensor and alternator
Perform wiggle test on harnesses while monitoring live data for intermittent drops

Signal parameters

MAP sensor signal typically ~0.5–4.5 V depending on manifold pressure (near 0.5 V = high vacuum, near 4.5 V = high pressure); intermittent drops below expected idle range indicate fault
MAP sensor reference typically 5.0 V ±0.25 V (key on) — loss or sag of this reference causes incorrect MAP voltage
Sensor ground should be low resistance to chassis/PCM ground; intermittent grounding can pull signal low
Charging system voltage should be ~13.5–14.7 V with engine running; alternator control circuit faults may show voltage dips or regulator inoperative
Intermittent low-voltage events may be brief — use data logger or scope to capture events not shown on steady-state DMM

Diagnostic algorithm

Retrieve and document freeze-frame, freeze‑frame conditions, and all stored codes. Note battery voltage during fault.
Visually inspect MAP sensor and alternator harnesses, connectors, and grounds for damage, corrosion, or loose pins. Repair or secure as needed.
With key ON (engine off), backprobe MAP sensor connector: verify 5V reference present and solid, check signal voltage and sensor ground continuity to PCM.
Start engine and monitor MAP sensor voltage and battery/charging voltage with a scan tool. Reproduce symptoms; perform wiggle tests on harness and connectors while observing live data.
If intermittent low signal appears, use an oscilloscope to capture the MAP signal and reference/ground to determine whether the drop is in the sensor, wiring, or PCM input.
Test alternator charging and field/control circuits: check alternator lower/control circuit resistance, inspect alternator connector and wiring for shorts to ground, and verify regulator operation per manufacturer procedure.
Check fuses/fusible links and any intermediate modules that supply or protect the MAP reference or alternator control circuits.
If wiring and external components check good, consider substituting known-good MAP sensor or alternator (or bench testing them) before replacing the PCM.
After repairs, clear codes and perform a road test with data logging to confirm the intermittent low-voltage condition no longer occurs and code does not return.
If intermittent faults persist, consult manufacturer service information and wiring diagrams for shared circuits and test PCM input drivers.

Likely causes

Intermittent open/short to ground on MAP signal or alternator lower/control circuit
Loose or corroded connector at MAP sensor or alternator harness
Faulty 5V reference or signal ground to MAP sensor
Faulty alternator field/low control circuit or internal regulator intermittently pulling voltage down
PCM input/output driver intermittently shorting or losing reference

Fault status

⚠️ Status

Intermittent low-voltage detected on dual‑alternator lower control circuit or MAP sensor circuit. Check wiring, grounds, sensor and alternator control for intermittent faults.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.5 hours

Repair manuals