Preliminary Inspection

WARNING: This page is about a different car, the 2002 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.

Trouble shooting of a cruise control system complaint begins with verification of the customer problem. Perform Customer Problem Analysis (Cruise Control System Check List). See Fig 1.
Perform Basic Inspection. See BASIC INSPECTION under SELF-DIAGNOSTIC SYSTEM.
Use Cruise Control System Check List and perform System Operation Check. See SYSTEM OPERATION CHECK . If customer problem is confirmed during system operation check, go to step 5. If customer problem is not confirmed during system operation check, go to next step.
If problem does not occur, review conditions under which problem occurred for customer. For example, if the problem occurs on rainy days or during high humidity conditions, sprinkle water onto vehicle and see if malfunction occurs. DO NOT sprinkle water directly into engine compartment or onto electronic components. Visually inspect for signs of mechanical and electrical damage. Inspect for blown fuses and damaged relays. Inspect for loose or corroded connections, damaged wiring harnesses and/or switches. Check for a broken or partially broken wire inside insulation, which could cause system malfunction but prove good in a continuity/voltage check with system disconnected. Ensure any aftermarket electronic equipment is properly installed. If fault is found, repair as necessary. If problem still cannot be created, go to next step.
Retrieve diagnostic trouble codes. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. Record and compare codes output to the codes output during Preliminary Diagnostic Trouble Code Check.
If DTCs are the same as those recorded in step 2 of PRELIMINARY DIAGNOSTIC TROUBLE CODE CHECK and symptom is present, problem is current in diagnostic circuit, diagnose and repair DTC. See DIAGNOSTIC TROUBLE CODE INDEX table under SELF-DIAGNOSTIC SYSTEM. If DTCs are not the same as those recorded in step 2 of PRELIMINARY DIAGNOSTIC TROUBLE CODE CHECK and no symptoms are present, original DTC was a history code signifying that problem occurred in circuit some time in the past or is a secondary problem. If DTCs are not the same as those recorded in step 2 of PRELIMINARY DIAGNOSTIC TROUBLE CODE CHECK , but symptom is still present, problem is still occurring somewhere other than current diagnostic circuit. Perform Cruise Control Input Signal Check to determine which circuit fault may be located. See CRUISE CONTROL INPUT SIGNAL CHECK . With results from Cruise Control Input Signal Check in hand, diagnose by symptom. See SYMPTOM INDEX table under SYSTEM TESTS. When performing symptom diagnosis, it may be necessary to perform pin voltage tests on cruise control ECU to ensure proper voltage or input/output signals exist. See PIN VOLTAGE TESTS when directed by diagnostic procedures.
After problem has been identified and repaired, confirm repairs have resolved complaint. See CONFIRMATION TEST under SELF-DIAGNOSTIC SYSTEM.

Fig 1: Customer Problem Analysis (Cruise Control System Check List)