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 MANUALSPLYMOUTH1984HORIZON BASE, 1.6 AREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 9 (ENGINE CONTROLS - TESTS W/CODES - 3.5L)SELF-DIAGNOSTIC SYSTEMSERVICE PRECAUTIONS
1984 Plymouth Horizon Base, 1.6 A
Service Precautions
1984 Plymouth Horizon Base, 1.6 ASECTION Service Precautions
WARNING: This page is about a different car, the 1994 Eagle Vision, 1994 Dodge Intrepid, 1994 Chrysler New Yorker, 1994 Chrysler LHS, and 1994 Chrysler Concorde. However, it is still accessible from the selected car via links, so may be relevant.
Before proceeding with diagnosis, the following precautions must be followed:
- ALWAYS relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components. See FUEL PRESSURE RELEASE .
- When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in the GENERAL INFORMATION section before disconnecting battery.
- Vehicle must have a fully charged battery and functional charging system.
- Probe PCM 60-pin connector from pin side. DO NOT backprobe PCM connector.
- DO NOT cause short circuits when performing electrical tests. This will set additional trouble codes, making diagnosis of original problem more difficult.
- DO NOT use a test light instead of a voltmeter.
- When checking for spark, ensure coil wire is NO more than 1/4" from ground. If coil wire is more than 1/4" from ground, damage to vehicle electronics and/or PCM may result.
- DO NOT prolong testing of fuel injectors or engine may hydrostatically (liquid) lock.
- Always repair lowest trouble code number (CHECK ENGINE light) or first trouble code message displayed (DRB) first.
- Always perform verification procedure test after repairs are made.
- Always disconnect DRB after use.
- Always disconnect DRB before charging battery.
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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.