Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSPLYMOUTH1994LASER RS TURBO, AWD, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - TESTS W/CODES - 1.8LDIAGNOSTIC CHARTSTEST DR-21A - CHECKING DRB COMMUNICATION
1994 Plymouth Laser RS Turbo, AWD, Automatic
Test Dr-21A - Checking DRB Communication
1994 Plymouth Laser RS Turbo, AWD, AutomaticSECTION Test Dr-21A - Checking DRB Communication
NOTE:
For connector terminal identification, see CONNECTOR IDENTIFICATION . For appropriate wiring diagram, see WIRING DIAGRAMS .
- If DRB screen is not blank, go to step 4). If DRB screen is blank, disconnect DRB adapter from diagnostic connector. Turn ignition switch to OFF position. Measure resistance between diagnostic connector terminal No. 12 (Black wire) and ground. See Figure. If resistance is more than 10 ohms, repair Black wire for an open to ground. Perform TEST VER-2 .
- If resistance is less than 10 ohms, inspect DRB adapter Red battery lead for good battery connection. Repair as required. Perform TEST VER-2. If battery connection is okay, connect a known good DRB adapter to diagnostic connector.
- Reconnect DRB. If display is not blank, perform TEST DR-1A. If display is blank, connect a known good DRB to adapter. If display is not blank, perform TEST DR-1A . If display is blank, insert a known good program cartridge into DRB. DRB display should be operational. Perform TEST DR-1A. If DRB display is not operational, go to step 1).
- Disconnect DRB adapter from diagnostic connector. Turn ignition switch to OFF position. Disconnect Electronic Control Unit (ECU) 24-pin connector. Measure resistance of Yellow wire between ECU 24-pin connector terminal No. 1 and diagnostic connector terminal No. 1. See Figure.
- If resistance is more than 10 ohms, repair open Yellow wire. Perform TEST VER-2 . If resistance is less than 10 ohms, measure resistance between ECU 24-pin connector terminal No. 1 (Yellow wire) and ground. If resistance is less than 10 ohms, repair Yellow wire for a short to ground. Perform TEST VER-2.
- If resistance is more than 10 ohms, measure resistance of White wire between ECU 24-pin connector terminal No. 2 and diagnostic connector terminal No. 10. See Figure. If resistance is more than 10 ohms, repair open White wire. Perform TEST VER-2. If resistance is less than 10 ohms, measure resistance between ECU 24-pin connector terminal No. 2 (White wire) and ground.
- If resistance is less than 10 ohms, repair White wire for a short to ground. Perform TEST VER-2. If resistance is more than 10 ohms, connect a known good DRB adapter to diagnostic connector. Attempt to read faults. If DRB is able to read faults, perform TEST DR-1A.
- If DRB is not able to read faults, connect a known good DRB to adapter. Try to read faults. If DRB is able to read faults, perform TEST DR-1A . If DRB is not able to read faults, insert a known good program cartridge in DRB.
- Try to read faults. If DRB is not able to read faults, replace ECU. Perform TEST VER-2. If DRB is able to read faults, perform TEST DR-1A.
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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.