Learning Guide CHASSIS SPECIALIST ELECTRIC POWER STEERING COURSE NUMBER: W013-01
Chassis Specialist : Electric Power Steering Notice Due to the wide range of vehicles makes and models, the information given during the class will be general in nature and should not be taken as specific to any vehicle/unit. Please consult manufacturer specifications for the correct number/specifications and repair procedures for the vehicle you are testing. This document is meant to be used as a guideline only.
Chassis Specialist : Electric Power Steering Table of Contents Table of Contents ................................................................................................................................... iii Introduction ............................................................................................................................................. 1 Objectives ..............................................................................................................................
Chassis Specialist : Electric Power Steering Introduction OBJECTIVES Upon successful completion of this lesson, participants will be able to: Describe the operation and control methods used on OEM electric power steering systems Perform diagnosis and repair of the electric power steering systems Perform system setup after repairs and alignments RATIONALE Due to fuel economy and noise concerns vehicle manufacturers have developed electric power steering systems.
Chassis Specialist : Electric Power Steering Electric Power Steering Systems Power steering systems were originally developed in the early 1950’s; the first production vehicle being the 1951 Chrysler Imperial. These systems were hydraulic with a pump being driven by the vehicle’s engine. As it is difficult to turn the steering wheel at low speeds, automobile manufacturers were forced to install very large steering wheels.
Chassis Specialist : Electric Power Steering EPS controller will determine the appropriate assist level. This system is compact but very expensive; any failure of the motor, sensor or internal mechanical devices makes the steering gear replacement necessary. The double pinion EPS system has the motor assembly located in a separate housing. The pinion motor drives a second pinion gear to assist the pinion attached at the column.
Chassis Specialist : Electric Power Steering One of the benefits of EPS is an increase in fuel economy, according to Ford this increase can be up to one mile per gallon. On a conventional power steering system, the pump will always be operating whenever the engine is running. With the EPS system there is no parasitic draw on the engine. The electrical power the system uses is readily available and draws on the system only when required.
Chassis Specialist : Electric Power Steering EPS Motor The EPS motor can either be a brushless or brushed reversible motor. Depending upon the motor’s location it will provide assist at the steering gear or the steering column. The motors used in nonHybrid vehicles are 12 volts DC and will be rated between 35 and 80 amps. On some applications the motor will also be a part of the power steering control module (PSCM).
Chassis Specialist : Electric Power Steering The compensating coil is used to buffer changes in the electrical current caused by temperature, varying electrical loads and system voltage providing the detecting coil with a constant voltage with which to accurately detect steering wheel movement. The detecting sensor is a dual analogue sensor that uses a 5 volt reference and is valid between 0.25 and 4.75 volts.
Chassis Specialist : Electric Power Steering STEERING POSITION SENSOR SIGNAL 1 STEERING WHEEL POSITION SENSOR SIGNAL 2 Steering Wheel Position Sensor Signals Power Steering Control Module (PSCM) The power steering control module (PSCM) is the brain of the system.
Chassis Specialist : Electric Power Steering Operation and Diagnosis In this section the various EPS systems will be discussed. This section will be broken down by vehicle manufacturer—Ford, General Motors, Honda and Toyota. FORD ELECTRIC POWER STEERING ASSIST SYSTEM (EPAS) Ford refers to the electric power steering system as Electronic Power Assist Steering or EPAS.
Chassis Specialist : Electric Power Steering B2477 Module Configuration Failure B3104 Steering Shaft Position sensor Malfunction C2000 Steering Angle Sensor Not Calibrated U0100 Loss of Communications with the ECM/PCM U0101 Loss of Communications with the TCM U0155 Loss of Communications with the Instrument Panel Cluster (IPC) U2023 Fault Received from External Node C1277 Steering Wheel Angle 1 and 2 Circuit Failure C1278 Steering Wheel Angle 1 and 2 Signal Failure For trouble codes B1317
Chassis Specialist : Electric Power Steering EPAS Column Assembly Initialization 1. Have the vehicle on a flat level surface with the transmission in PARK 2. Place the steering wheel in the straight ahead position 3. Connect the scan tool to the diagnostic link connector (DLC) 4. Turn the ignition to RUN 5. Select ESP sensor calibration on the scan tool menu and follow the on screen instructions 6. Clear all power steering system trouble codes from all modules 7.
Chassis Specialist : Electric Power Steering The torque sensor is the main input that the PSCM uses to determine the steering direction and the amount of assist to provide. The steering column input and output shafts are separated by a torsion bar that has the sensor mounted to it. The sensor is a dual signal sensor similar to the model that Ford uses. The sensor is a 5 volt sensor that operates between 0.25 and 4.75 volts.
Chassis Specialist : Electric Power Steering The EPS motor and PSCM are serviced as an assembly separate from the steering column. The PSCM assembly is calibrated specific to the vehicle. The calibration is referred to as the Steering Tuning Selection. System voltage is critical to the operation and is constantly monitored. The EPS motor is rated at 65 amps. Due to the large current required to operate the EPS motor, the PSCM has a built in thermal protection feature.
Chassis Specialist : Electric Power Steering The Koyo system used by the Cobalt, G5, Equinox, Torrent, Ion and Vue is basically the same as the Delphi system with the exception of the steering wheel position sensor, the PSCM is separate from the motor and the motor itself is not serviceable. The EPS motor is rated at 58 amps. Cobalt Steering System The Koyo PSCM contains 8 steering calibrations which are based on the vehicle’s options.
Chassis Specialist : Electric Power Steering RUN/START FUSE BLOCKUNDERHOOD POWER DISTRIBUTION SCHEMATICS IN WIRING SYSTEMS EPS FUSE 60A EPS STR WHL CNTRL Fuse 19 POWER DISTRIBUTION 2A 60A SCHEMATICS IN BODY CONTROL MODULE (BCM) WIRING SYSTEMS DLC Schematics in Computer/Integrating Systems POWER DISTRIBUTION SCHEMATICS IN WIRING SYSTEMS Battery Positive Voltage Ignition 1 Voltage LEFT ASSIST MOTOR CONTROL High High Speed Speed GMLAN GMLAN Serial Data Serial Data Bus+ Bus- High High Speed Speed GM
Chassis Specialist : Electric Power Steering Trouble Codes Description C0000 Vehicle Speed Information Circuit C0176 System Thermal Error C0460 Steering Position Sensor C0475 Electric Steering Motor Circuit C0545 Steering Wheel Torque Input Sensor C0550 Electronic Control Unit (ECU) Performance C0896 Device Voltage/Range Performance C0897 Device Power Mode-ing Error C0899 Device Voltage Low C0900 Device Voltage High C0845 Device Ignition 1 Circuit (Cobalt and G5) C0895 Device Volta
Chassis Specialist : Electric Power Steering C1508 Internal Motor Circuit Malfunction (Saturn Astra) C1512 Temperature Sensor Circuit (Saturn Astra) C1517 Overheat Protection Mode Malfunction (Saturn Astra) C1523 System Voltage (Saturn Astra) C1525 Engine Running Signal (Saturn Astra) C1527 Motor Circuit (Saturn Astra) C1528 Motor speed Invalid Signal Malfunction (Saturn Astra) C1529 Motor Circuit (Saturn Astra) C1550 ECU failure (Saturn Astra) On the Delphi system, if there is a fault wi
Chassis Specialist : Electric Power Steering Inspect the Lower Control Arms Poor Steering Return Inspect the Steering Knuckles and Strut Bearings Inspect the Ball Joints and Axles Steering Wheel when Turning jerks Inspect for Worn Suspension Components Binding in the Intermediate Shaft, Steering Gear or Column Inspect the EPS motor for excessive Heat Steering Wheel Kickback Inspect for Loose Column and rack bolts Inspect for Damaged Tie Rod Ends Delphi System Initialization The EPS system requires a
Chassis Specialist : Electric Power Steering Torque Sensor Calibration 1. On a flat level surface install the scan tool 2. Turn the ignition ON with the engine OFF 3. Centre the steering wheel. After centreing the steering wheel do not touch the steering wheel and verify there is no force being applied to the steering wheel or system. 4. Build the vehicle and select the special functions menu in the steering system menu 5. Highlight the Steering Torque Sensor Calibration and press enter.
Chassis Specialist : Electric Power Steering Koyo System Initialization On the Koyo system, the PSCM is serviced separately, all other components are serviced as an assembly. If the vehicle comes in with a steering complaint refer to the Delphi chart above for information with the following exception: To test the Koyo system for a clunk, rattle noise or vibration at low speeds, remove the 60 amp EPS fuse—usually located in the under hood junction block.
Chassis Specialist : Electric Power Steering 11. Observe the scan tool and wait until the display reads “Calibration Complete”. Enter the steering system data list and verify the steering wheel position (if equipped) reads 0 +/- 5 degrees. If the steering wheel position sensor reads outside of the parameter, the display should read “Procedure Failed”, try to repeat the calibration again. 12.
Chassis Specialist : Electric Power Steering One common customer complaint on both systems is a no steering assist concern. This usually happens in a parking lot manoeuvre or when a vehicle is being used for driver instruction. If the steering wheel is held on the steering stop, the PSCM will command maximum current to the motor. If the steering wheel is held in this position for several seconds, the PSCM will limit the current to the EPS to protect against excessive heat.
Chassis Specialist : Electric Power Steering the fluid is low top up with the special Saturn power steering fluid for this vehicle. Do not overfill the system. A scan tool must be used to access system diagnostic trouble codes and perform the steering control module setup. HONDA ELECTRIC POWER STEERING (EPS) SYSTEM Honda uses a rack drive electric motor for the EPS system used on the Civic Si. The system consists of an EPS control module, EPS motor, torque sensor and a centre take off steering gear.
Chassis Specialist : Electric Power Steering EPS Indicator Light Operation Whenever the EPS indicator is illuminated, the vehicle will have reduced or no power steering assist. The light will illuminate briefly for a bulb check on start up and will illuminate anytime a system fault is detected. The light will illuminate if the EPS controller is defective or loses battery power but no diagnostic codes will be set. If a torque sensor code is set, the light will remain on until the DTC is cleared.
Chassis Specialist : Electric Power Steering Flash Code Possible Component 11 High or Low Ignition Voltage 12 High or Low System Voltage 21 Vehicle Speed Signal 22 Engine Speed Signal 31 Torque Sensor Neutral Position 32 Internal ECU Failure 33 Internal EPS Motor Fault 34 Power or Fail Safe Relay Stuck On 35 EPS Control Unit Internal Circuit Malfunction 36 EPS Control Unit Output Circuit Fault 37 EPS Control Unit Step Up Circuit Fault 51 Torque Sensor Fault 61 Open or Short in th
Chassis Specialist : Electric Power Steering Trouble codes can be cleared by using the Service Check Signal Circuit Method. The steps must be followed exactly in order to clear the codes. With the ignition switch OFF ground pin 9 of the DLC The vehicle must be on the ground with the steering wheel in the straight ahead position Turn the ignition switch to the ON position. The EPS indicator should be illuminated for 6 seconds.
Chassis Specialist : Electric Power Steering The EPS system can be checked for the correct Level of Assist. Verify the vehicle has the original equipment tires and wheels and that the tire inflation is correct Start the engine and let the engine idle Attach a spring scale (commercially available) to the steering wheel.
Chassis Specialist : Electric Power Steering TOYOTA ELECTRIC POWER STEERING (EPS) SYSTEM Toyota also uses a steering column with an electric assisting motor. Torque is generated through the motor and a reducing gear installed in the steering column shaft. The EPS ECU monitors the vehicle speed, the skid control ECU and torque sensor to determine the correct amount of assist to apply. The assist level is adjusted so there is more assist at lower speeds and virtually no assist at high speed.
Chassis Specialist : Electric Power Steering CODE 21 (ON for half second) ON Combination Meter OFF SECONDS NORMAL CODE ON Power Steering Warning Light OFF SECONDS Page 28
Chassis Specialist : Electric Power Steering DTC/ DTC Description Possible Component C1511/11 Torque Sensor Circuit 1 Torque Sensor or ECU C1512/11 Torque Sensor Circuit 2 Torque Sensor or ECU C1513/11 Excessive Torque Sensor Deviation Torque Sensor or ECU C1514/11 Torque Sensor Supply Voltage Torque Sensor or ECU C1521/25 Short in the EPS Motor Circuit ECU C1524/24 Motor Terminal Voltage Malfunction Torque Sensor or ECU C1528/12 Motor Rotation Angle Sensor Torque Sensor or ECU C153
Chassis Specialist : Electric Power Steering To clear the system DTC’s without a scan tool With the ignition switch in the OFF position jumper terminals 4 and 12 of the DLC together Turn the ignition switch ON with the engine OFF Remove the jumper wire from terminal 4 then reconnect it. Repeat this procedure 4 or more times within 8 seconds Verify the normal code flashes. The normal code can be identified by a short flash followed 0.
Chassis Specialist : Electric Power Steering Glossary BCM Body Control Module CAN Controller Area Network CIM Column Integration Module DC Direct Current DLC Diagnostic Link Connector DTC Diagnostic Trouble Code ECM Electronic Control Module ECU Electronic Control Unit EHPS Electric Hydraulic Power Steering (Saturn) EPAS Electronic Power assist Steering (Ford) EPS Electronic Power Steering ESP Electronic Stability Programme GMLAN General Motors Local Area Network IPC Instrument P
