U0154 Lost Communication with the Restraint Presence Sensor Control Unit

U0154 Lost Communication with the Restraint Presence Sensor Control Unit

OBD-II DTC Datasheet

Lost Communication With Restraints, Passenger Occupancy Sensor Control Module

What does this mean?

This is a generic communication system diagnostic trouble code that applies to most makes and models of vehicles. Manufacturers may include, but are not limited to, Dodge, Jeep, Ford, Land Rover, etc.

This code means that the passenger control system control module (ROSCM) 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 ROSCM is usually located under the passenger seat. It accepts input from various sensors, some of which are directly connected to it, and some are sent over a bus communication system. The most important of these sensor inputs are the seat weight sensors. These inputs allow the module to determine who or what is occupying the passenger seat, and in some cases how close they are to the passenger's airbag. ROSCM takes no action; it simply provides data to the restraint controller after it has determined who or what is occupying the passenger seat. The Restraint Controller 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.

Severity and symptoms

The seriousness in this case is always serious because of the safety issues that arise from a non-functional restraint control system. Safety is ANYONE'S concern when servicing these systems because they can continue to operate even if the warning lights are on. ALWAYS treat these systems as if they can operate at all times.

Symptoms of a U0154 engine code may include:

• Airbag light is on or flashing
• Passenger airbag indicator is on

reasons

Usually the reason for installing this code is:

• Open in CAN + bus circuit
• CAN bus break - electrical circuit
• Short circuit to power in any CAN bus circuit
• Short to ground in any CAN bus circuit
• 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 related to the tire, vehicle identification number (VIN), or battery / ignition, diagnose them first. Misdiagnosis is known to occur if you diagnose the U0154 code before any of the major codes are thoroughly diagnosed and rejected.

If your scan tool can access the trouble codes and the only code you are getting from other modules is U0154, try accessing the ROSCM. If you can access the codes from the ROSCM, then the U0154 code is either intermittent or a memory code. If you cannot access the ROSCM, then the U0154 code that the other modules are setting is active and the problem already exists.

The most common fault is loss of power or grounding to the ROSCM module.

Check all fuses supplying the ROSCM on this vehicle. Check all the grounds for ROSKM. 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 U0154 returns or you can contact the ROSCM. If no code returns or connectivity is restored, the problem is most likely a fuse / connection issue.

BEFORE DISCONNECTING THE ROSCM CONNECTORS, MAKE SURE THE SYSTEM IS TURNED OFF ACCORDING TO THE MANUFACTURER'S 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, locate the CAN bus connections on your specific vehicle, most importantly the ROSCM connector, which is usually behind the dash or behind the panel on the right B pillar. Before disconnecting the connector on the ROSCM, disconnect the negative battery cable. 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 dielectric silicone grease where the terminals touch.

Before connecting the connectors back to the ROSCM, perform these few voltage checks. You will need access to a digital volt ohm meter (DVOM). Make sure you have power and ground at the ROSCM. Access the wiring diagram and determine where the main power and ground sources enter the ROSCM. Reconnect the battery before continuing, with the ROSCM still disconnected. Connect the red lead from your volt meter to each B+ (battery voltage) source entering the ROSCM connector, and the black lead from your volt meter to a good ground (if unsure, the negative battery post always works). You should see a battery voltage reading. Make sure you have a good ground. Connect the red lead from your volt meter to the battery positive (B+) and the black lead to each ground circuit. Once again, you should see battery voltage with each connection. If not, troubleshoot the power or ground circuit.

Before proceeding, check the wiring diagram and see if you have one or both of these different communication circuits in the ROSCM; Carry out the checks related to the circuits in your vehicle.

Next, check the two communication circuits. Find the CAN C+ (or HSCAN+) circuit and the CAN C- (or HSCAN – circuit). With the black lead of the voltmeter connected to a good ground, connect the red lead to CAN C+. With the key on and the engine off, you should see about 2.6 volts with slight fluctuations. Then connect the red lead of the voltmeter to the CAN C- circuit. You should see about 2.4 volts with slight fluctuations.

Next, check the other two communication circuits. Find CAN B+ (or MSCAN+ circuit) and CAN B- (or MSCAN – circuit). With the black lead of the voltmeter connected to a good ground, connect the red lead to CAN B+. With the key on and the engine off, you should see about 0.5 volts with slight fluctuations. Then connect the red lead of the 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 the U0154 trouble code, the only correct thing to do is to seek help from a trained automotive diagnostician, as this will indicate a faulty ROSCM module. Most of these ROSCM modules must be programmed or calibrated for the vehicle in order to be installed correctly.

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