P2774 code definition
Exclusive to AWD or 4WD vehicles, a P2774 code means the vehicle’s PCM has detected a problem in the low switch circuit for 4WD. A hard code has been registered and the malfunction indicator lamp (MIL) has illuminated. If you ever find a P2774 code in a 2WD vehicle, there could be a programming issue or a defective PCM.
What the P2774 code means
The P2774 code is an indicator of a problem in the actuator switch circuit for 4WD. This 4WD switch controls the actuation of the 4WD system, and changes between gear ratios in the transfer case – 2WD high, 2WD low, neutral, 4WD high and 4WD low.
What causes the P2774 code?
A P2774 code can be caused by an actuator failure or a failed 4WD switch. Other problems can include:
- Faulty sensors
- Faulty solenoids
- Faulty switches
- Defective wiring harness or connectors
What are the symptoms of the P2774 code?
Symptoms of a P2774 code can include:
- Illuminated MIL
- Failure to shift from 2wd to 4wd low or high, or back again
- Engine stalls while stopped and in gear
- Harsh shifts
- Complete transfer case failure
How does a mechanic diagnose the P2774 code?
Many vehicles, especially older models, rely on a combination of engine vacuum and electronics to actuate shifts in the transfer case. Most newer vehicles, on the other hand, use full-electronic systems of sensors and solenoids to shift from low to high range or back again. Other systems are designed with solenoids that lock front hubs into place, with manual levers to allow shifting for the transfer case. Still others (on AWD vehicles) can automatically switch from 2WD to AWD according to road conditions.
Regardless, practically all OBD II equipped vehicles are designed with an electronic transfer case module that interacts with other control modules and enacts transfer case and front differential changes. 4WD switches may vary, but for on-demand systems, the switch is the “on/off” variety and is mounted in the interior, within reach of the driver.
Inspect all wiring and connectors, and repair/replace any damaged, shorted, disconnected or corroded wiring, connectors or components if found.
After any repairs of wiring, connectors and components (including fuses), retest the system. If everything seems to be in working order, connect a scanner or code reader to the vehicle’s diagnostic port, recording all stored codes and data.
Clear codes and operate the vehicle to see if codes return. If not, there may be an intermittent condition which may need to be allowed to worsen again to make an accurate diagnosis.
Should the code return right away, find a factory wiring schematic with connector details. Check for battery voltage on the 4WD switch’s input side, using your digital volt/ohmmeter. If no voltage can be found on the switch’s input side, disconnect any related control modules and check for continuity between the input circuit at the clutch position sensor and the system fuse.
Repair any open or shorted circuits.
If voltage is present on the 4WD switch’s input side, use the scanner to enable the 4WD system and check voltage readings on the switch’s output side.
If voltage is present on the input side but not the output side, with 4WD engaged, a faulty 4WD switch could be the culprit. Replace the switch if needed, and retest the system afterward. If voltage is present at the clutch position sensor’s output circuit, check for voltage at the actuator for 4WD.
If no voltage is present, check between the switch and PCM for resistance and circuit continuity, and compare your readings to manufacturer’s specs.
Repair any shorted or open circuits/connectors that are faulty, and refer to the factory wiring schematic to ensure you don’t miss any circuits. If readings all agree with factory specs, suspect the PCM itself but remember that faulty PCMs are rare.
Common mistakes when diagnosing the P2774 code
Too many times, P2774 codes have been misdiagnosed, resulting in a complete (very expensive) rebuild or replacement of the transfer case, when a proper diagnosis and replacement of a component may well have fixed the problem.
How serious is the P2774 code?
The P2774 code can result in a vehicle that’s completely disabled, stranding a driver by the side of the road.
What repairs can fix the P2774 code?
- Replacement of the 4WD switch or activator
- Replacement of failed sensors
- Replacement of solenoids or switches
- Overhaul of wiring harness and/or connectors
Additional comments for consideration regarding the P2774 code
As with any repair job, a P2774 code calls for a thorough investigation of possible causes and a factory service guide and wiring schematic as a guide. Be certain to disconnect any related control modules before testing the 4WD switch and circuits.
Need help with a P2774 code?
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