OBD-II Trouble Code Technical Description
The circuit for Transmission Mode Switch B is experiencing a high electrical condition.
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) that is commonly found in OBD-II vehicles, including those from GMC, Chevrolet, Ford, Buick, Dodge, and others. However, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
The Transmission Control Module (TCM) is responsible for monitoring all the sensors and switches involved in the operation of the transmission. In modern automatic transmissions, there are various features and functions that are controlled by the TCM, such as cruise control and tow/haul mode. The tow/haul mode is used to adjust the transmission ratios and shift patterns to accommodate different loads and towing demands. The proper functioning of the mode switch is crucial for the operation of the tow/haul function and other related systems. It is important to identify the specific mode switch that is associated with the fault code and matches the make and model of the vehicle.
The letter “B” in this code can have different definitions or distinguishing factors, which may vary depending on the specific circumstances. It is essential to consult the appropriate service information before conducting any troubleshooting steps to ensure accurate diagnosis and resolution of uncommon or obscure faults. This article serves as a general learning tool due to its broad nature.
The ECM (Engine Control Module) will activate the MIL (Malfunction Indicator Lamp) and display the P071F code, along with related codes (P071D, P071E), when it detects a malfunction in the mode switch. In most cases, tow/haul switches are located on or near the shift lever, either as a button on the end of the lever for stalk-style shifters or on the dash for console-style shifters. The location of the switch can vary significantly between vehicles, so it is advisable to consult the service manual for specific instructions.
The P071F code indicates a high electrical condition in the “B” transmission mode switch circuit, as detected by the ECM and/or TCM.
Here is an example of a stalk-mounted transmission tow/haul mode switch:
What is the severity of this DTC?
The severity of this DTC depends on the specific mode switch associated with the vehicle’s fault. In the case of tow/haul switches, the severity is considered low. However, it is advisable to avoid heavy loads and towing to prevent unnecessary stress on the transmission and its components. It is important to exercise common sense in this regard.
What are some of the symptoms of the code?
Symptoms of a P071F trouble code may include:
What are some of the common causes of the code?
The causes of the P071F code may include:
What are some P071F troubleshooting steps?
Basic Step #1
Depending on the available tools and references, the starting point for troubleshooting may vary. If the scanner has monitoring capabilities (DATA STREAM), it is possible to monitor the values and operation of the mode switch. Toggle the switch on and off to check if the scanner recognizes the inputs. Keep in mind that there may be a slight delay, so allow a few seconds when monitoring switches.
If the mode switch appears inoperative according to the scanner, it may be possible to rule out the circuit by jumping some pins at the switch’s connector. If the circuit is ruled out in this manner and the switch remains inoperative, proceed to test the switch itself. These are general guidelines, and with a moderately capable scan tool, troubleshooting can be relatively straightforward if the specific criteria are known. Refer to the service manual for specifications and procedures.
Basic Step #2
If possible, test the switch itself. In most cases, these switches are simple on/off style switches that signal the appropriate module(s) (e.g., TCM, BCM, ECM) about the towing/load requirements, allowing for modified shift patterns. A continuity test with an ohm meter can determine the functionality of the sensor. Keep in mind that these sensors are sometimes integrated into the shift lever, so it is important to research the specific connectors and pins that need to be monitored with a multimeter.
NOTE: As with any transmission fault, always ensure that fluid levels and quality are adequate and well-maintained.
