U016A Lost communication with global positioning system module

OBD-II DTC Datasheet

Lost Communication With Global Positioning System Module

What does this mean?

This is a generic communications system diagnostic trouble code that applies to most makes and models of OBD-II vehicles.

This code means that the Global Positioning System Module (GPSM) and other control modules on the vehicle are not communicating with each other. The circuitry most commonly used for communication is known as Controller Area Bus communication, or simply the CAN bus.

Modules communicate with each other over a network, just like the network you have at home or work. Car manufacturers use several networked systems. Prior to 2004, the most common (non-exhaustive) inter-module communication systems were the serial communication interface, or SCI; SAE J1850 or PCI bus; and Chrysler Collision Detection, or CCD. The most common system used after 2004 is known as Controller Area Network communication, or simply the CAN bus (also used until 2004 on a small segment of vehicles). Without this CAN bus, control modules cannot communicate and your scan tool may or may not receive information from the vehicle, depending on which circuit is affected.

The Global Positioning System Module (GPSM) is usually located behind the dashboard, usually in the center of the vehicle, although in some vehicles it may be installed in the trunk. It receives input from various sensors, some of which are directly connected to it, and most are sent over a bus communication system from the powertrain control module (PCM). These inputs allow the module to display correct route information by calculating the vehicle position and sending this information over the data bus to the navigation module or to the instrument cluster / main display system.

Troubleshooting steps may vary depending on the manufacturer, the type of communication system, the number of wires, and the colors of the wires in the communication system.

Code severity and symptoms

The severity in this case can be serious if the GPSM sends incorrect data to the display module / system, thereby providing incorrect navigation information.

Symptoms of a U016A code may include:

Navigation system no information / blank screen
Navigation system does not work

reasons

Usually the reason for installing this code is:

Open on CAN bus + or - circuit
Short to ground or ground in any CAN bus circuit
No power or ground to GPSM
Rarely - the control module is faulty

Diagnostic and repair procedures

A good place to start with ALL electrical diagnostics is to check the Technical Service Bulletins (TSB) for your vehicle. The problem you are facing may be known to others in the field. A known fix may have been released by the manufacturer and can save you time and money during diagnostics.

It is assumed that a code reader is available to you at this point, as you may have been able to access the codes up until now. See if there were any other DTCs related to bus communication or battery / ignition. If so, you should diagnose them first, as misdiagnosis is known to occur if you diagnose the U016A code before any of the underlying codes are thoroughly diagnosed and corrected.

If the only code you get from other modules is U016A, try accessing the GPSM. If you can access codes from GPSM, then code U016A is either intermittent or a memory code. If the GPSM cannot be accessed, then code U016A set by other modules is active and the problem already exists.

The most common failure is a circuit failure that results in a loss of power or ground to the global positioning system module.

Check all fuses supplying power to the GPSM on this vehicle. Check all grounds for GPSM. Locate grounding attachment points on the vehicle and make sure these connections are clean and secure. If necessary, remove them, take a small wire bristle brush and baking soda / water solution and clean each one, both the connector and the place where it connects.

If any repairs have been made, clear the diagnostic trouble codes from any modules that set the code in memory and see if you can now communicate with the GPSM. If communication with GPSM recovers, the problem is most likely a fuse / connection issue.

If the code returns or communication with the module still cannot be established, locate the CAN bus communication connections on your vehicle, most importantly the GPSM connector, which is usually located behind the dashboard, usually in the center of the vehicle, although in some vehicles it may be installed in the trunk. Disconnect the negative battery cable before disconnecting the connector from the GPSM. Once detected, visually inspect the connectors and wiring. Look for scratches, scuffs, exposed wires, burn marks, or molten plastic.

Disconnect the connectors and carefully inspect the terminals (metal parts) inside the connectors. See if they look burnt or have a green tint indicating corrosion. If you need to clean the terminals, use an electrical contact cleaner and a plastic bristle brush. Allow to dry and apply electrical grease where the terminals touch.

Perform these few voltage checks before reconnecting the connectors to the GPSM. You will need access to a digital volt/ohmmeter (DVOM). Make sure the GPSM has power and ground. Access the wiring diagram and determine where the main power and ground sources enter the GPSM. Connect the battery before continuing with GPSM still disabled. Connect the red lead of your voltmeter to each B+ (battery voltage) power source included in the GPSM connector, and the black lead of your voltmeter to a good ground (if unsure, battery negative always works). You should see the battery voltage reading. Make sure you have a good reason. Connect the red lead of the voltmeter to the battery positive (B+) and the black lead to each ground circuit. Once again, you should see the battery voltage every time you connect. If not, repair the power or ground circuit.

Then check the two communication circuits. Locate CAN C+ (or HSCAN+) and CAN C- (or HSCAN - circuit). With the black wire of the voltmeter connected to a good ground, connect the red wire to CAN C+. With the key on and engine off, you should see about 2.6 volts with little fluctuation. Then connect the red wire of the voltmeter to the CAN C- circuit. You should see about 2.4 volts with little fluctuation. Other manufacturers show CAN C- at about 5V and an oscillating key with the engine off. Check your manufacturer's specifications.

If all tests pass and communication is still not possible, or if you are unable to reset DTC U016A, the only thing you can do is seek help from a trained automotive diagnostician as this may indicate a GPSM failure. Most of these GPSMs must be programmed or calibrated to fit properly in the vehicle.

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