P071E Transmission Mode Switch B Circuit Low

P071E Transmission Mode Switch B Circuit Low

OBD-II DTC Datasheet

Low signal level in the chain of the switch B transmission mode

What does this mean?

This is a generic powertrain diagnostic trouble code (DTC) and is commonly applied to OBD-II vehicles. This may include, but is not limited to, vehicles from GMC, Chevrolet, Ford, Buick, Dodge, etc. Despite the general nature, the exact repair steps may vary depending on the model year, make, model and transmission configuration.

The transmission control module (TCM) monitors all sensors and switches involved in the transmission. These days, automatic transmissions (also known as A / T) offer more convenience than ever before.

For example, cruise control is monitored and controlled by the TCM (among other possible modules) from time to time. The example I will be using in this article is the tow/traction mode, which allows the operator to change gear ratios and shift patterns to accommodate changing loads and/or towing requirements. Operation of this switch is required for the towing/carrying function to function among other systems that may be enabled. This will vary considerably between manufacturers, so make sure you know WHICH mode switch applies to your current fault, as well as the specific make and model.

The letter "B" in this code, in any case, in this case, can have several different definitions / distinguishing factors. They will be different in most cases, so be sure to obtain the appropriate service information before performing any invasive troubleshooting steps. This is not only important, but also necessary to accurately troubleshoot unclear or unusual faults. Use this as a learning tool given the general nature of the article.

The ECM turns on a malfunction indicator lamp (MIL) with a P071E and / or related codes (P071D, P071F) when a malfunction is detected in the mode switch. In most cases, when it comes to the tow / tow switch, they are located on or near the gear lever. On a toggle switch, this may be a button at the end of the lever. On console type switches, it may be on the dashboard. Another factor that varies considerably between vehicles, so refer to your service manual for location.

Transmission mode switch B circuit low code P071E is activated when the ECM (engine control module) and / or TCM detects a low voltage level in the transmission mode switch "B" circuit.

Example of a tow / traction switch on the transmission steering column switch:

What is the severity of this DTC?

The severity largely depends on which mode switch your vehicle is malfunctioning in. In the case of the tow / haul switches, I would say this is a low severity level. However, you can avoid heavy loads and / or towing. This can cause you to put unnecessary stress on the drivetrain and its components, so be sane here.

What are some of the symptoms of the code?

Symptoms of a P071E DTC may include:

• Mode switch does not work (e.g. tow / carry mode switch, sport mode switch, etc.)
• Intermittent and / or abnormal switch operation
• Ineffective gear shifting
• Low power under heavy load / towing
• No downshifting when torque is needed

What are some of the common causes for the code?

Reasons for this P071E code may include:

• Defective or damaged mode switch
• Corrosion causing high resistance (e.g. connectors, pins, ground, etc.)
• Wiring problem (e.g. worn out, open, short to power, short to ground, etc.)
• Defective gear lever
• TCM (Transmission Control Module) problem
• Fuse / box problem

What are some of the P071E troubleshooting steps?

Basic step # 1

Depending on what tools / reference materials you have at your disposal, your starting point may differ. However, if your scanner has any monitoring capabilities (DATA STREAM), you can monitor the values ​​and / or the operation of your particular mode switch. If so, turn the switch on and off to check if your scanner recognizes your input. There can be a delay here, so a few seconds delay is always a good idea when monitoring switches.

Moreover, if you find that the mode switch is not working according to your scanner, you can swap multiple pins on the mode switch connector to eliminate the circuit. If the circuit is ruled out this way and the switch is still not working, I would move on to testing the switch itself. Obviously these are general guidelines, but with a moderately capable scanning tool, troubleshooting MAY be painless if you know what you are looking for. Refer to your service manual for specifications / procedures.

Basic step # 2

If possible, check the switch itself. In most cases, these switches are only intended to signal the appropriate module (s) (e.g. TCM, BCM (Body Control Module), ECM, etc.) that are required for towing / loading so that it can implement modified gear shifting schemes. However, most of the ones I've come across are related to the on / off style. This means that a simple continuity check with an ohmmeter can determine the functionality of the sensor. Now these sensors are sometimes embedded in the gear lever, so be sure to research which connectors / pins you need to monitor with a multimeter.

NOTE: As with any transmission malfunction, always check that the fluid level and quality are adequate and maintained in good condition.

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