Ground problems
Ground problems are a common cause of electrical, ignition, charging, lighting, and drivability issues on the Pontiac Fiero.
Because the Fiero is now several decades old, poor grounds can result from corrosion, loose fasteners, damaged wires, previous repairs, paint, rust, or worn connectors.
Overview
A ground connection completes an electrical circuit by providing a return path to the battery negative terminal. If a ground is missing, loose, corroded, or high-resistance, electrical components may behave unpredictably.
Ground problems can affect many systems, including the starter, ignition system, fuel pump, ECM, sensors, gauges, lights, radiator fan, headlight system, and charging system.
Symptoms
Common symptoms of ground problems include:
- Slow cranking
- No-start condition
- Intermittent stalling
- Dim or flickering lights
- Strange gauge readings
- Erratic sensor readings
- Poor charging
- Headlight motor problems
- Fuel pump problems
- Intermittent electrical faults
- Blown fuses
- Components working only sometimes
- Electrical problems that change when other accessories are switched on
Common ground-related systems
Ground problems can affect:
- Battery
- Starter
- Alternator
- ECM
- Sensors
- Fuel pump
- Ignition module
- Headlights
- Instrument cluster
- Radiator fan
- Tail lights
Battery and engine grounds
The battery negative cable, engine ground straps, and chassis grounds are especially important. Poor engine or chassis grounding can cause starting problems, charging problems, ignition problems, and sensor errors.
Related topics:
ECM and sensor grounds
The ECM and sensors depend on clean, stable ground connections. Poor sensor grounds can cause incorrect readings and drivability problems.
Related topics:
- ECM
- Sensors
- MAP sensor
- Coolant temperature sensor
- Throttle position sensor
- Oxygen sensor
- ALDL diagnostics
Lighting grounds
Lighting problems may be caused by poor grounds, especially if lights are dim, backfeeding, flickering, or behaving strangely when other lights are switched on.
Related topics:
Diagnosis
Ground diagnosis may include:
- Inspecting battery cables and terminals.
- Inspecting engine-to-chassis ground straps.
- Inspecting visible ground wires and attachment points.
- Cleaning corrosion from ground terminals.
- Checking for loose fasteners.
- Measuring voltage drop under load.
- Checking continuity only as a preliminary test.
- Comparing symptoms when electrical loads are switched on.
- Inspecting for previous wiring repairs or added accessories.
Voltage drop testing
A ground may show continuity but still fail under load. Voltage drop testing is often more useful than a simple continuity test.
A high voltage drop across a ground path indicates resistance in the cable, connector, fastener, or attachment point.
Repair
Common repairs include cleaning ground points, tightening fasteners, replacing damaged wires, replacing battery cables, adding supplemental ground straps, repairing connectors, and removing paint or corrosion from contact surfaces.
Notes
Ground problems can imitate many other failures. Before replacing expensive electrical parts, inspect and test the relevant power and ground connections.