SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSCHEVROLET1995FORWARD CONTROL 7.4 NREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - 5.7LSELF-DIAGNOSTIC SYSTEMSCAN TESTER USAGE
1995 Chevrolet Forward Control 7.4 N

Scan Tester Usage

1995 Chevrolet Forward Control 7.4 NSECTION Scan Tester Usage
NOTE: Before connecting scan tester, check diagnostic system and ensure accurate information is received by scan tester. Perform DIAGNOSTIC CIRCUIT (GASOLINE) CHECK in BASIC TESTING - 5.7L article. If vehicle does not pass diagnostic circuit check, information received by scan tester may be invalid.

The scan tester is a specialized tester which can diagnose on-board computer control systems by providing access to circuit voltage information without crawling under dash or hood to backprobe sensors and connectors. scan testers reduce diagnostic time by furnishing input data (voltage signals) which can be compared to specification parameters. See SCAN TESTER DATA .

Scan testers also furnish information on output device (solenoids and motors) status. However, status parameters are only an indication output signals have been sent to devices by the control module. They do not indicate whether devices respond properly to that signal. This must be verified at output device using a voltmeter or test light.

NOTE: On models not using "P" series codes, Code 12 should always exist when DLC test terminal is grounded with key on and engine off, but it may not be indicated by all makes of scan tester.

If trouble codes are not present, a problem may still exist. Driveability-related problems with codes displayed occur about 20 percent of the time, while driveability problems without codes occur about 80 percent of the time. Out-of-calibration sensors WILL NOT set a trouble code, but WILL cause driveability problems. A scan tester is the 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 TESTER DATA .

NOTE: Information obtained by scan tester is only as accurate as the tester itself. If erroneous voltage signals are suspected, verify tester information using a digital voltmeter and wiring schematic. If non-existent codes are displayed, turn ignition off and remove tester. Turn ignition on and ground DLC test terminal. If same codes are not flashed by Malfunction Indicator Light (MIL) as were indicated by scan tester, tester cannot be used on vehicle and information obtained by it will not be guaranteed accurate. If tested vehicle does not provide for grounding diagnostic test terminal, verify tester accuracy by connecting it to a known good vehicle.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.