Chassis / SAS

STEERING ANGLE SENSOR

Reports steering-wheel position, direction and rate to stability and ADAS systems.

SENSOR GUIDE25/86

Identify the circuit first

ONE NAME.
DIFFERENT SIGNALS.

Pin count is a clue, not proof. Confirm the exact architecture before resistance testing, applying voltage or judging the waveform.

TYPE 01CONSTRUCTION VARIANT

Optical encoder

Confirm wiring, pin count and service information before testing.

A coded disc and optical receiver calculate angle and direction.

Reading the signal

Good waveform

Logic levels and edge transitions are consistent with the installed circuit. Pulse timing changes in the specified way as the input changes; intended index gaps or encoded features repeat correctly.

Faulty waveform

Missing or extra edges, weak switching levels, intermittent pulse loss or a stuck level can indicate supply, ground, wiring, target or sensor problems. A steady level can be normal when the target is stationary. Decode encoded signals using the correct protocol.

TYPE-SPECIFIC TESTS

+ Inspect clock-spring alignment, scan angle through multiple turns and perform zero calibration.

+ Verify the specified supply, ground, bias or termination before judging the signal.

+ Repeat the test through the complete operating range.

EXPECTED

✓ Output matches this construction type

✓ Stable levels and repeatable response

✓ Agreement with related scan data

COMMON FAULTS

— Incorrect test method for the sensor type

— Supply, ground or signal-circuit fault

— Installation, target or calibration concern

TYPE 02CONSTRUCTION VARIANT

Hall / magnetoresistive

Confirm wiring, pin count and service information before testing.

Magnetic sensing provides contactless absolute or incremental position.

Reading the signal

Good waveform

Logic levels and edge transitions are consistent with the installed circuit. Pulse timing changes in the specified way as the input changes; intended index gaps or encoded features repeat correctly.

Faulty waveform

Missing or extra edges, weak switching levels, intermittent pulse loss or a stuck level can indicate supply, ground, wiring, target or sensor problems. A steady level can be normal when the target is stationary. Decode encoded signals using the correct protocol.

TYPE-SPECIFIC TESTS

+ Graph angle and rate smoothly through the complete range and compare redundant tracks.

+ Verify the specified supply, ground, bias or termination before judging the signal.

+ Repeat the test through the complete operating range.

EXPECTED

✓ Output matches this construction type

✓ Stable levels and repeatable response

✓ Agreement with related scan data

COMMON FAULTS

— Incorrect test method for the sensor type

— Supply, ground or signal-circuit fault

— Installation, target or calibration concern

TYPE 03CONSTRUCTION VARIANT

Integrated EPS/network sensor

Confirm wiring, pin count and service information before testing.

Angle may be calculated inside the steering module and transmitted over CAN.

Reading the signal

Good waveform

Compare the measured signal with the specified input or command under the same operating conditions. Levels, timing and repeatability should match the installed design and a suitable verified reference. There is no universal waveform or scale for every version of this component.

Faulty waveform

An unexplained dropout, missing response, excessive noise or mismatch between command and feedback warrants further testing. First rule out a changed physical condition, incorrect probe reference, supply loss and an unsuitable scope setting; an unusual trace alone does not identify a failed component.

TYPE-SPECIFIC TESTS

+ Verify module power, network data, center calibration and alignment before replacement.

+ Verify the specified supply, ground, bias or termination before judging the signal.

+ Repeat the test through the complete operating range.

EXPECTED

✓ Output matches this construction type

✓ Stable levels and repeatable response

✓ Agreement with related scan data

COMMON FAULTS

— Incorrect test method for the sensor type

— Supply, ground or signal-circuit fault

— Installation, target or calibration concern

Correct theory and operation

HOW IT
WORKS.

Understand the sensing method, circuit and controller strategy before interpreting data or replacing the component.

01

Measured condition

Reports steering-wheel position, direction and rate to stability and ADAS systems.

02

Signal type

Digital networked sensor. Internal electronics condition the sensing element and transmit calculated data through a dedicated digital line or vehicle network.

03

Controller use

The receiving controller checks range, rationality and rate of change against related inputs before setting a fault or substituting a value.

04

Installation matters

Mounting, target condition, air gap, contamination, temperature, shielding or calibration may affect the result even when the circuit is intact.

Common mistakes

AVOID THE
FALSE CLUE.

COMPLETE TEST SEQUENCE

  1. Perform a complete module scan before disconnecting anything.
  2. Verify powers, grounds, wake-up and communication.
  3. Compare the sensor PID with related physical measurements.
  4. Follow calibration, initialization and replacement procedures.
  5. Repeat the original operating condition and confirm the repair.
DO NOT CONDEMN THE SENSOR

Prove its supply, ground, signal path, physical input and calibration before replacement. Vehicle-specific specifications always win.

SENSOR LIBRARYReturn to all sensors→

Diagnostic details

Purpose

Stability-control and driver-assistance systems use steering angle to determine the direction the driver intends the vehicle to travel.

Scan tool data

  • Steering-angle rate
  • SAS calibration status
  • Yaw rate
  • Lateral acceleration

Failure symptoms

  • Stability-control warning
  • Traction-control warning
  • Incorrect stability intervention
  • ADAS calibration problems

Related DTCs

  • Manufacturer-specific chassis codes are common
  • Steering-angle plausibility codes
  • Calibration codes
  • Communication codes

Diagnostic tips

  • Check wheel alignment and steering-wheel centering.
  • Calibration may be required after alignment or steering repairs.
  • A non-zero value does not automatically indicate sensor failure.

Construction & type-specific testing

Identify the installed design before testing. Construction, signal format and redundant channels are separate attributes; use only the procedure for the actual component.

Optical Steering-Angle Encoder

A coded optical target is read by light emitters and receivers.

Operating principle

  • A coded optical target is read by light emitters and receivers.

Circuit identification

Application-specific; see wiring below

Wiring

  • Usually part of a powered module; network and calibration requirements vary.

Expected readings

  • Angle and direction change consistently, with a valid center and multi-turn position where supported.

Multimeter testing

  • Compare angle data through permitted steering movement and check calibration and module communication.

Oscilloscope setup

  • Identify the output interface and approved test points before connecting. Set the range, coupling and probes for that circuit.

Oscilloscope testing

  • Compare angle data through permitted steering movement and check calibration and module communication.
  • Follow steering-column and restraint-system precautions. Do not dismantle a clockspring for this test.

Waveform interpretation

Angle and direction change consistently, with a valid center and multi-turn position where supported. No universal known-good waveform is specified for this design.

Common failures

  • Connection, supply or signal-path faults where applicable
  • Damage, installation error or loss of calibration appropriate to this design

Diagnostic tips

  • Follow steering-column and restraint-system precautions. Do not dismantle a clockspring for this test.
  • Construction, output format and number of redundant channels are separate attributes.
Magnetic Steering-Angle Sensor

Hall or magnetoresistive elements detect the position of magnetic targets.

Operating principle

  • Hall or magnetoresistive elements detect the position of magnetic targets.

Circuit identification

Application-specific; see wiring below

Wiring

  • Usually part of a powered module; network and calibration requirements vary.

Expected readings

  • Angle and direction change consistently, with a valid center and multi-turn position where supported.

Multimeter testing

  • Compare angle data through permitted steering movement and check calibration and module communication.

Oscilloscope setup

  • Identify the output interface and approved test points before connecting. Set the range, coupling and probes for that circuit.

Oscilloscope testing

  • Compare angle data through permitted steering movement and check calibration and module communication.
  • Follow steering-column and restraint-system precautions. Do not dismantle a clockspring for this test.

Waveform interpretation

Angle and direction change consistently, with a valid center and multi-turn position where supported. No universal known-good waveform is specified for this design.

Common failures

  • Connection, supply or signal-path faults where applicable
  • Damage, installation error or loss of calibration appropriate to this design

Diagnostic tips

  • Follow steering-column and restraint-system precautions. Do not dismantle a clockspring for this test.
  • Construction, output format and number of redundant channels are separate attributes.