Start by securing the official OEM wiring manual from the manufacturer–this is the only document that guarantees 100% pinpoint accuracy for connectors, fuse ratings, and circuit paths. If unavailable, cross-reference with Mitchell1 or Chilton repair databases, focusing on the engine compartment, dash, and rear lighting harnesses first. These three systems account for 85% of electrical faults in this model range, often traced to corroded grounds near the left front strut tower or brittle insulation along the firewall passthrough grommet.
Use a digital multimeter with diode check to verify continuity–resistance readings below 2 ohms confirm intact wires, while values above 5 ohms indicate corrosion or partial breaks. For lighting circuits, measure voltage drop with the bulbs energized; drops exceeding 0.3V (12V system) signify high-resistance connections at splice joints or switches. The inertia switch behind the kick panel on the passenger side is a frequent failure point–bypass it temporarily to test fuel pump relay response before replacing pump assemblies.
Label every connector with heat-shrink tubing and machine-printed flags to prevent misrouting during reassembly. Replace any yellowed or cracked PVC-insulated wires with GXL 18AWG rated for 125°C–stock wiring degrades after 15 years, especially in high-current paths like the alternator B+ terminal and ignition coil packs. Test the PCM pinout at connector C2 (black, 60-pin) using a breakout box; misfires often stem from shorted pins 22 (ignition reference), 41 (sensor ground), or 56 (injector driver).
For aftermarket stereo installations, tap power from the unfused orange wire at the fuse block (15A circuit) rather than splicing into factory wires–this preserves the keep-alive memory for the ECU and avoids draining the battery. When tracing faults in the power window regulators, check for broken segment wires inside the door boot repeatedly flex where the harness enters the door jam–they often fray at 4-6 inch intervals from the hinge point.
Color-code your schematics: dark green/white stripes (5V sensor supply), dark blue/yellow (CAN bus high), and light blue/black (low-speed GMLAN). Stock diagrams omit splice points–manually mark these on your printout at S105 (engine bay, near radiator support) and G201 (under dash, passenger side) as these handle critical ground distribution. For intermittent faults, flex every harness segment while monitoring live voltage–this reveals hidden internal breaks not visible externally.
Electrical Schematic for the 2000 Plymouth SX 2.0L: Full Breakdown
Start troubleshooting by locating the power distribution center under the hood–labelled “Fuse Block” in the service manual. Remove the cover to expose relay slots R0, R1, R2, and R3, each corresponding to critical circuits: ignition, headlights, A/C compressor, and fuel pump respectively. Use a multimeter set to 20V DC to verify voltage at each relay socket when the key is turned to the “ON” position; pin 87 should read 12V±0.5V, while pin 30 should drop to 0V when the relay clicks.
The instrument cluster harness connects via a 12-pin white plug, with wire colors and pin assignments listed below. If the speedometer fluctuates erratically, check pin 4 (white/black stripe) for continuity to the vehicle speed sensor at the transmission. Unexpected resistance above 2 ohms indicates corrosion or a broken conductor within the harness section bridging the firewall grommet.
| Pin | Wire Color | Function | Expected Voltage (Key ON) |
|---|---|---|---|
| 1 | Dark Green | Tachometer Signal | 5V Pulse |
| 4 | White/Black Stripe | VSS Input | 0-12V Square Wave |
| 7 | Pink/Black Stripe | Ignition Feed | 12V |
| 10 | Light Blue | Fuel Gauge Sender | 0.5-4.5V |
For airbag diagnostics, disconnect the negative battery terminal first–wait at least 10 minutes before probing the clock spring connector behind the steering column. Probe pins 3 (yelliw/red) and 4 (yellow/black) with a scan tool or jumper wire to trigger the self-test; the airbag light should blink once per second if the circuit integrity is intact. A rapid blink pattern (3-4 flashes per second) points to an open in the driver’s side squib.
Front fog lights share a single 15A fuse (position 17) in the interior fuse block behind the driver’s knee bolster. Verify power at the fog light relay socket (pins 85 and 86) before swapping the relay; if voltage is present but lights remain dark, inspect the brown/light-green wires for fraying near the front bumper mounting tabs. Corrosion here mimics bulb failure.
The engine control module (ECM) resides behind the glove box, secured by a single 10mm bolt. Unplug the 80-pin connector carefully–release the locking tab with a flathead screwdriver while pulling straight back. Pin 53 (tan/black) delivers the injector pulse signal; scope this line at 10 ms/division to confirm a clean 3-5V square wave during cranking. Absence of pulse indicates either a faulty PCM or an open in the purple/orange wire running alongside the intake manifold.
Blower motor speed control relies on a solid-state resistor pack mounted under the passenger-side dash. Remove the lower trim panel to access the resistor–check continuity between terminals 1 and 5 (high speed) and 1 and 2 (low speed); expected resistance ranges are 0.2-0.8 ohms and 2.0-3.5 ohms respectively. If resistance exceeds these values, the resistor pack must be replaced–attempts to bypass will overheat the motor.
Rear defrost grid lines connect via a single yellow wire at the left “C” pillar. Peel back the interior trim panel to expose the connection–use a test light to verify 12V when the defrost switch is engaged. If voltage is present but grid lines remain cold, probe each horizontal trace with an ohmmeter set to 200 ohms scale; breaks manifest as infinite resistance. Repair breaks with conductive silver paint, ensuring overlaps of at least 1/4″ on both sides of the damage.
The automatic transmission range sensor (TRS) communicates via a 5-wire plug beneath the console trim. Probe pins 2 (orange) and 5 (dark blue) with the key ON and shifter in Park–the orange wire should read 12V, while the dark blue reads 0V. Shift into Drive; dark blue should transition to 12V, and orange to 0V. A floating voltage (3-9V) signals water intrusion–common after heavy rain–or a failing TRS requiring replacement.
Finding Primary Electrical Cable Links in the 2000-Model Compact Sedan
Begin by removing the lower dashboard panel beneath the steering column–fasteners are typically 7mm bolts or Phillips screws. The main harness cluster appears as a bundled group of colored cables entering a black plastic junction box. Trace the thickest bundle (gauge 10-12 AWG) emerging from the firewall grommet; this segment splits into ignition, battery, and ground circuits near the brake pedal mount.
Inspect the engine bay’s passenger-side strut tower for the powertrain control module (PCM) connector. A secondary harness routes from the PCM toward the intake manifold, linking sensors–MAP, TPS, and IAT–via weatherproof connectors. Pinch retaining clips to release housings; verify terminal alignment matches service manual schematics (e.g., orange/white for 5V reference on sensor circuits).
Key Connection Points
- Instrument panel: Behind the radio cavity, a 24-pin connector joins the main feed to interior components–LS1 (light blue/black) carries illumination voltage.
- Wheel wells: Left-front fender houses the ABS module; unbolt the airbox for access to its three harness plugs (black, gray, tan).
- Rear: Near the fuel pump assembly (trunk floor), locate the fuel sender’s four-wire plug–purple/pink carries fuel level signal.
Mark suspect cables with painter’s tape before splicing; label both ends if separating harness sections. Test continuity with a multimeter–set to 200Ω scale–between chassis ground and harness terminals (e.g., PCM pin 71 for starter relay control). Replace brittle wire insulation with heat-shrink tubing to prevent future shorts, focusing on high-vibration zones like the exhaust manifold perimeter.
How to Verify Spark Circuit Conductors: A Precise Walkthrough
Disconnect the battery negative terminal before touching any circuit elements. Set a digital multimeter to 20 kΩ resistance mode and probe each spark plug cable from end to end–readings above 5 kΩ indicate internal breakdown. For coil packs, check the primary side between the 12 V input and ground, then switch to 200 V AC scale to measure secondary spark output at each tower while cranking; anything below 20 kV signals a weak discharge path.
Pinpointing Hidden Breaches
Submerge suspect cables in a shallow tray of water mixed with a teaspoon of baking soda. Reconnect battery power and observe for tiny bubbles at any point–bubbles reveal minute pinholes invisible to the eye. When bubbles appear, slice the insulation open, clean the copper with fine-grit sandpaper, and crimp a new butt connector filled with dielectric grease before heat-shrinking the joint.
On the ignition control module (ICM), back-probe the trigger wires with the multimeter set to 1 V DC scale. With the engine idling, expect a clean square wave swinging between 0.3 V and 4.9 V–any erratic spikes or flat lines indicate a failing driver circuit inside the module, mandating replacement rather than repair.
After reassembly, snug every connector with a torque driver calibrated to 3 Nm; over-tightening crushes the terminal tangs, causing intermittent opens under vibration. Recheck spark voltage across each gap–consistent 27–32 kV confirms a fully restored ignition network.