P1105

Code

CHRYSLER P — Powertrain

Secondary Vacuum Sensor Circuit

Brand: CHRYSLER

Type: P — Powertrain

Views: UK: 39 EN: 58 RU: 61

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Page language: EN

Causes

Open or short in sensor wiring harness
Corroded, damaged or loose connector/pins at sensor or PCM
Failed/contaminated secondary vacuum sensor
Vacuum hose leak or restriction affecting sensor reading
Poor or missing ground or reference voltage
Blown fuse or relay supplying sensor circuit

Symptoms

Malfunction Indicator Lamp (MIL/Check Engine) illuminated
Rough idle or stalling (if vacuum signal used for idle control)
Reduced engine performance or drivability issues
Possible poor fuel economy or increased emissions
Brake assist or accessory effects if sensor monitors booster vacuum (rare/vehicle dependent)

What to check

Retrieve trouble codes and freeze-frame data with a scan tool; confirm P1105 is current
Visually inspect sensor, connector, wiring harness, and vacuum hoses for damage, corrosion or disconnection
Backprobe the sensor connector to verify reference voltage, ground, and sensor output with key ON and engine OFF
Wiggle test wiring while watching live data to try to reproduce fault
Check continuity and resistance of wiring between sensor and PCM pins
Use a handheld vacuum pump to apply vacuum while monitoring sensor output for proper response

Signal parameters

Reference supply: typically 5.0 V (check vehicle spec)
Ground: near 0 V (good engine/PCM ground)
Sensor output: generally within 0.5–4.5 V depending on vacuum level (consult vehicle-specific values)
Manifold vacuum typical at idle: ~15–22 inHg (vehicle dependent) — sensor voltage should change smoothly with applied vacuum
Wiring continuity to PCM: open circuit indicates high resistance/failed wire; expected low ohms (

Diagnostic algorithm

Connect a OBD-II scan tool, record P1105 and any related codes, note freeze-frame data and current sensor PID values.
Visually inspect the sensor, connector, and vacuum hoses for obvious damage, oil contamination, or disconnected lines. Repair as needed.
With ignition ON (engine OFF), backprobe the sensor connector: verify reference voltage (~5 V), check ground, and measure sensor output. Compare to expected ranges.
Start engine and monitor live sensor output while watching for unstable or out-of-range values. Perform a wiggle test of wiring to identify intermittent faults.
Use a handheld vacuum pump to apply vacuum to the sensor while observing output; the voltage should change smoothly and proportionally. No change or erratic response indicates sensor or wiring fault.
If reference or ground missing, trace wiring to the PCM and check continuity and for shorts to power or ground. Repair damaged wiring/connectors.
If wiring and power/ground are good but sensor output is incorrect, replace the secondary vacuum sensor and retest.
After repairs clear codes, verify the fault does not return after test drive. If P1105 returns and wiring/sensor checked, consider PCM diagnosis as last resort.

Likely causes

Damaged wiring or chafed insulation to the sensor
Corroded connector pin(s) at the sensor or PCM
Defective secondary vacuum sensor
Vacuum line disconnected, cracked, or clogged
Bad ground at sensor or control module

Fault status

⚠️ Status

P1105 — Secondary Vacuum Sensor Circuit: circuit malfunction or invalid sensor signal detected.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours

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