Trouble Shooting

NOTE: If problem is intermittent, check for faulty wiring and components by wiggling wiring harnesses and components (DO NOT vigorously wiggle relays).

Ensure actuator cable is not too loose (may cause vehicle to lose speed when driving uphill) or too tight (causes high idle speed).
Check for Diagnostic Trouble Codes (DTCs). See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. If any DTCs are set, perform appropriate procedure under DIAGNOSTIC TESTS . If no DTCs are set, go to SYMPTOM DIAGNOSIS table.
If cruise control ECU is suspected of not receiving an input from a switch or vehicle speed sensor, check input signal circuits. See INPUT SIGNAL CIRCUITS under CIRCUIT TESTS. If problem is still present after all testing, replace cruise control ECU.

SYMPTOM DIAGNOSIS

Problem

Inspect

Speed Cannot Be Set Or Unwanted Canceling

No DTCs Are Set (Normal DTC)

⁽¹⁾ Main Switch Circuit (Cruise Control Switch)
⁽²⁾ Vehicle Speed Sensor
⁽²⁾⁽³⁾ Control Switch Circuit (Cruise Control Switch)
⁽¹⁾ Stoplight Switch Circuit
⁽¹⁾ Park/Neutral Position Switch Circuit
⁽²⁾ Actuator Motor Circuit
⁽⁴⁾ Actuator Control Cable
⁽⁵⁾ Cruise Control ECU

DTC Does Not Display

⁽¹⁾ ECU Power Source Circuit
⁽⁵⁾ Cruise Control ECU

Actual Speed Differs From Set Speed

⁽⁴⁾ Actuator Control Cable
⁽²⁾ Vehicle Speed Signal Abnormal
⁽¹⁾ Electronically Controlled Transmission Communication Circuit
⁽²⁾ Actuator Motor Circuit
⁽²⁾ Idle Signal Circuit (Main Throttle Position Sensor)
⁽⁵⁾ Cruise Control ECU

Shifts Between 3rd Gear & Overdrive Uphill (Hurting)

⁽¹⁾ Electronically Controlled Transmission Communication Circuit
⁽⁵⁾ Cruise Control ECU

Speed Setting Does Not Cancel

When Brake Pedal Is Pressed

⁽⁴⁾ Actuator Control Cable
⁽¹⁾ Stoplight Switch Circuit
⁽²⁾ Actuator Motor Circuit
⁽⁵⁾ Cruise Control ECU

When Shifting Into Neutral

⁽⁴⁾ Actuator Control Cable
⁽¹⁾ Park/Neutral Position Switch Circuit
⁽²⁾ Actuator Motor Circuit
⁽⁵⁾ Cruise Control ECU

Cruise Control Switch Does Not Operate

⁽⁴⁾ Actuator Control Cable
⁽²⁾⁽³⁾ Control Switch Circuit
⁽²⁾ Actuator Motor Circuit
⁽⁵⁾ Cruise Control ECU

At Speeds Less Than 25 MPH Speed Can Be Set Or CANCEL Does Not Operate

⁽⁴⁾ Actuator Control Cable
⁽²⁾ Vehicle Speed Signal Abnormal
⁽²⁾ Actuator Motor Circuit
⁽⁵⁾ Cruise Control ECU

Poor Response In ACC & RES

⁽⁴⁾ Actuator Control Cable
⁽¹⁾ Electronically Controlled Transmission Communication Circuit
⁽²⁾ Actuator Motor Circuit
⁽⁵⁾ Cruise Control ECU

Overdrive Does Not RESUME

⁽¹⁾ Electronically Controlled Transmission Communication Circuit
⁽⁵⁾ Cruise Control ECU

DTC

Memory Is Erased

⁽⁵⁾ Cruise Control ECU

Cannot Be Displayed Or Are Displayed When Should Not Be

⁽¹⁾ Diagnostic Circuit
⁽⁵⁾ Cruise Control ECU

CRUISE Indicator Light Remains Illuminated Or Will Not Illuminate

⁽¹⁾ Cruise Main Indicator Light Switch Circuit
⁽⁵⁾ Cruise Control ECU

⁽¹⁾	Perform appropriate circuit test under CIRCUIT TESTS . If more than one circuit test is listed, perform tests in order listed.

⁽²⁾	Perform appropriate DTC test under DIAGNOSTIC TESTS . See DIAGNOSTIC TROUBLE CODE (DTC) DEFINITION table.

⁽³⁾	On ES300 only.

⁽⁴⁾	Inspect actuator control cable. See ACTUATOR CONTROL CABLE under ADJUSTMENTS.

⁽⁵⁾	Perform CRUISE CONTROL ECU PIN VOLTAGE TESTS under COMPONENT TESTS.