Technical Description of OBD-II Trouble Code
Circuit for the Four Wheel Drive (4WD) Switch
What does that signify?
This is a standard diagnostic trouble code (DTC) for powertrain and is applicable to many OBD-II vehicles (1996-newer). This includes vehicles from various manufacturers such as Chrysler, Ford, Jeep, General Motors, Dodge, Chevrolet, Mercedes, etc. Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration.
OBD-II trouble code P0836 and related codes P0837, P0838, and P0839 are associated with the circuit for the four wheel drive (4WD) switch. This circuit is also known as the transfer case control circuit.
The purpose of the 4WD switch circuit is to allow the driver to select the activation of the 4WD system and change the gear ratios of the transfer case as required, including two wheel high, two wheel low, neutral, four wheel high, and four wheel low, based on the configuration.
When the PCM or TCM detects improper voltage or resistance within the 4WD switch circuit, code P0836 will be set and the check engine light, 4WD malfunction light, or both may illuminate.
A four wheel drive selector switch:
What is the severity of this DTC?
The severity of this code is typically moderate, but problems with the 4WD switch circuit can be severe if the transfer case is stuck in low gear. This can cause unwanted stress on internal transmission and engine components, requiring immediate attention. In some cases, the vehicle may not move or shift into gear at all.
What are some of the symptoms of the code?
Symptoms of a P0836 trouble code may include:
What are some of the common causes of the code?
Causes for this P0836 code may include:
What are some P0836 troubleshooting steps?
The first step in the troubleshooting process for any malfunction is to research the Technical Service Bulletins (TSB’s) for the specific vehicle by year, model, and power plant. In some cases, this can save a lot of time in the long run by providing guidance in the right direction.
The second step is to check the transmission and transfer case fluid to ensure it is at the appropriate level and in good condition. Then, locate all components associated with the 4WD switch circuit and inspect them for any obvious physical damage. Depending on the specific vehicle, this circuit may include several components such as the transfer case, switches, solenoids, the PCM, and TCM. Conduct a thorough visual inspection of the associated wiring to check for any obvious defects such as scraping, rubbing, bare wires, or burn spots. Next, check the connectors and connections for security, corrosion, and damaged pins. This process should include all wiring connectors and connections to all components, including the PCM and TCM. Consult the specific technical data for the vehicle to verify the configuration and see if a fuse or fuse-able link is part of the circuit.
Advanced Steps
The advanced steps are highly specific to the vehicle and require advanced equipment to perform accurately. These procedures involve using a digital multi meter and referring to the specific technical references for the vehicle.
Voltage Checks
The reference voltage and acceptable ranges may vary depending on the specific vehicle and circuit configuration. The specific technical data will include troubleshooting charts and the appropriate sequence to follow for an accurate diagnosis.
If this process reveals the absence of a power source or ground, continuity testing may be necessary to check the integrity of the wiring, connectors, and other components. Continuity tests should always be performed with the power removed from the circuit, and the normal readings for wiring and connections should be 0 ohms of resistance. Resistance or lack of continuity indicates faulty wiring that is open or shorted and must be repaired or replaced. A continuity test from the PCM or TCM to the frame will confirm the serviceability of ground straps and ground wires. The presence of resistance indicates a loose connection or possible corrosion.
What are some common repairs for this code?
Common Mistake
Hopefully, the information in this article has been helpful in guiding you to address the problem with your 4WD switch circuit fault code. This article is purely informational, and the specific technical data and service bulletins for your vehicle should always take precedence.
