Scan Tester Specifications - Efi Chevrolet Corsica I

SCAN TESTER USAGE

Note. Prior to connection of scan tester to vehicle, diagnostic system should be checked to determine if system is operating properly and if information received by scan tester will be accurate. This is done by performing appropriate DIAGNOSTIC CIRCUIT CHECK for that system. Refer to the appropriate TESTS/CODES article in this section. If vehicle does not pass diagnostic circuit check, information received by scan tester may be invalid.

CCC Scan tester is a specialized tester which, when plugged into ALDL, can be used to diagnose on-board computer control systems by providing instant access to circuit voltage information without need to crawl under dash or hood to back-probe sensors and connectors. Scan testers cut down diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters (see SCAN DATA tables). They also furnish information on output device (solenoids and motors) status. Status parameters, however, are only an indication that output signals have been sent to devices by the ECM. It does not indicate if devices have responded properly to that signal. This will need to be verified at output device using a voltmeter or test light.

Note. Code 12 should always exist when ALDL is grounded with key on and engine not running but may not be indicated by all makes of scan testers.

If trouble codes are not present, this is not an indication that there is not a problem. CCC related problems are about 20 percent codes and 80 percent driveability. Sensors that are out of specification WILL NOT set a trouble code but WILL cause driveability problems. Use of a scan tester is easiest method of checking sensor specifications and other data parameters. Tester is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters. See SCAN DATA tables in this section.

Note. Information obtained by scan tester is only as accurate as the tester itself. If erroneous voltage signals are suspected, it will be necessary to verify tester information using a digital voltmeter and wiring schematic. If non-existent codes are in evidence, turn ignition off, remove tester, turn ignition on and ground ALDL "test" terminal. If same codes are not flashed by "SERVICE ENGINE SOON" light that were indicated by scan tester, tester cannot be used on vehicle and information obtained by it will not be guaranteed accurate.

THROTTLE BODY INJECTION - SCAN DATA SPECIFICATIONS

Note. Information contained in the following table is typical of readings taken on vehicle with engine idling, upper radiator hose hot, closed throttle, transmission in Park or Neutral, "closed loop" status achieved and all accessories off (except as noted in tables). Data parameters are updated every 1 1/4 seconds. On systems using P-4 computers, parameter updates are virtually instantaneous. Not all devices & systems are used on all models.

THROTTLE BODY INJECTION

PORT FUEL INJECTION - SCAN DATA SPECIFICATIONS

Note. Information contained in the following table is typical of readings taken on vehicle with engine idling, upper radiator hose hot, closed throttle, transmission in Park or Neutral, "closed loop" status achieved and all accessories off (except as noted in tables). Data parameters are updated every 1 1/4 seconds. On systems using P-4 computers, parameter updates are virtually instantaneous. Not all devices & systems are used on all models.

PORT FUEL INJECTION

Note. If ECM displays data but engine fails to start, proceed to chart A-3 in the TESTS W/ CODES article in this section.

Note. Condensed, general SYMPTOM DIAGNOSIS and INTERMITTENTS testing articles are located in the TROUBLE SHOOTING section. Also refer to the CEC TESTS W/O CODES article in this section.