U0170 Lost Communication With Sensor A Restraint System

U0170 Lost Communication With Sensor A Restraint System

OBD-II DTC Datasheet

Lost Communication With Restraint Sensor A

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 Restraint System Sensor A (RSS-A) 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.

Without this CAN bus, control modules cannot communicate and your scan tool may not receive information from the vehicle, depending on which circuit is involved.

The restraint sensor a is usually located behind the dashboard, usually in the center of the vehicle. It receives input data from various sensors, some of which are directly connected to it, most of which are transmitted via a bus communication system. The most important of these sensor inputs are the collision or collision sensors. This input allows the module to determine when a collision has occurred or when the vehicle is simply slowing down quickly. The difference between the two is that RCM can take no action, can activate seat belt pretensioners, or activate pretensioners and passive restraints / airbags.

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 is always serious due to the safety issues that arise in a non-functional restraint control system. Safety is ANYONE's concern when you service these systems because they can continue to operate even when the warning lights are on. ALWAYS treat these systems as if they could work at any time.

Symptoms of a U0170 code may include:

• Airbag light is on or flashing

reasons

Usually the reason for installing this code is:

• Open in CAN + bus circuit
• Open in the CAN bus - electrical circuit
• Short circuit to power in any CAN bus circuit
• Short to ground in any CAN bus circuit
• No power or ground to RSS-A module
• Rarely - the control module is faulty

Diagnostic and repair procedures

A good starting point is always to check the Technical Service Bulletins (TSB) for your particular vehicle. Your problem may be a known issue with a known manufacturer-released fix and could save you time and money while troubleshooting.

First, look for other DTCs. If any of these are bus communication or battery / ignition related, diagnose them first. Misdiagnosis is known to occur if you diagnose the U0170 code before any of the major codes are thoroughly diagnosed and rejected.

If your scan tool can access trouble codes and the only code you are getting from other modules is U0170, try accessing the Restraint System Sensor A (RSS-A). If you can access codes from RSS-A, then code U0170 is either intermittent or a memory code. If RSS-A cannot be accessed, then code U0170 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 restraint system sensor a.

Check all fuses supplying the RSS-A module on this vehicle. Check out all the reasons for RSS-A. Locate ground anchorage 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 DTCs from memory and see if U0170 returns or you can contact the RSS-A module. If no code returns or connectivity is restored, the problem is most likely a fuse / connection issue.

BEFORE DISCONNECTING THE RSS-A CONNECTORS, MAKE SURE THE SYSTEM TURNS OFF FOR PRODUCER PROCEDURES! Otherwise, POSSIBLE DAMAGE TO THE VEHICLE OR PERSONAL INJURY DUE TO UNINTENDED DEPLOYMENT OF THE AIR BAG. ALSO, THE AIRBAGS ARE DISCONNECTED DURING THE FOLLOWING TESTS AS A FINAL SAFETY MEASURE!

If the code returns, look for the CAN bus communication connections on your vehicle, especially the RSS-A connector, which is usually located behind the dashboard. Disconnect the negative battery cable before disconnecting the connector from the RSS-A module. 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 RSS-A. You will need access to a digital volt/ohmmeter (DVOM). Make sure RSS-A has power and ground. Access the wiring diagram and determine where the main powers and grounds enter the RSS-A. Before continuing, reconnect the battery with the RSS-A still disconnected. Connect the red lead of your voltmeter to each B+ (battery voltage) power supply included in the RSS-A 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.

Before proceeding, check the wiring diagram and check if you have one or both different communication circuits on the RCM; Perform the checks that apply to the circuits in your vehicle.

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.

Then check the other two communication circuits. Locate CAN B+ (or MSCAN + circuit) and CAN B- (or MSCAN - circuit). With the black wire of the voltmeter connected to a good ground, connect the red wire to CAN B+. With the key on and the engine off, you should see a voltage of about 0.5 volts with little fluctuation. Then connect the red lead of a voltmeter to the CAN B circuit. You should see about 4.4 volts with slight fluctuations.

If all tests pass and communication is still not possible, or you were unable to clear DTC U0170, the only thing to do is to seek help from a trained automotive diagnostician, as this will indicate an RSS-A failure. . Most of these RSS-A's must be programmed or calibrated to fit properly on the vehicle.

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