What Does P1159 Mean?
This code indicates a malfunction in the variable intake manifold motor (also known as an intake manifold runner control motor or tumble generator valve actuator). This motor actuates the variable-length intake runners or swirl flaps to optimize airflow at different RPM ranges. When the motor fails or its control circuit is faulty, the intake geometry cannot be adjusted, leading to reduced engine performance across certain RPM bands.
Common Causes
30%
Failed variable intake motor (burned-out coil, seized actuator)
25%
Intake manifold runner flaps stuck due to carbon buildup
20%
Open or shorted wiring in the variable intake motor circuit
15%
Corroded or disconnected connector at the intake motor
10%
PCM driver circuit failure for the variable intake motor
Diagnostic Steps
1
Measure resistance across the variable intake motor coil at the connector; compare to manufacturer specifications (typically 5-30 ohms).
2
Command the variable intake motor actuator on/off using a scan tool and listen/feel for actuator movement; no movement indicates a stuck mechanism or failed motor.
3
Inspect the wiring harness and connector for the variable intake motor; check for battery voltage and proper ground when commanded on.
4
Remove the intake manifold runner control assembly and check the flaps for carbon buildup or mechanical binding; clean or free as needed.
5
If the motor is electrically sound but mechanically seized, clean or replace the intake runner assembly. If electrically failed, replace the motor.
Estimated Repair Cost
$200 - $600
Parts + labor, varies by vehicle and location
This code indicates a malfunction in the variable intake manifold motor (also known as an intake manifold runner control motor or tumble generator valve actuator). This motor actuates the variable-length intake runners or swirl flaps to optimize airflow at different RPM ranges. When the motor fails ...
The most common cause of P1159 (Variable Intake Motor Malfunction) is: Failed variable intake motor (burned-out coil, seized actuator)
Typical repair costs for P1159 range from $200 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
No direct safety risk. The vehicle remains drivable but may experience reduced power at certain RPM ranges, slightly increased fuel consumption, and possible rough idle or hesitation during acceleration.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1159 to identify the root cause.
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Quick Info
Category
Powertrain
System
Intake Air Management
Difficulty
Type
Manufacturer
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