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.
SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSPONTIAC1990GRAND PRIX STE, 3.1 VREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - BASIC TESTINGNO START DIAGNOSISNO START - ENGINE CRANKS OKAY (PFI WITH IDI)IGNITION SYSTEM
1990 Pontiac Grand Prix STE, 3.1 V
Ignition System
1990 Pontiac Grand Prix STE, 3.1 VSECTION Ignition System
- Disconnect tachometer wire from IDI module (if equipped). A shorted tachometer will not allow vehicle to start. Temporarily remove IDI assembly and install spark plug Jumper Wires (J 36012). Check for adequate spark with Spark Tester (ST-125). Check for spark on 2 adjacent plug wires (1-2 or 3-4, not 2-3). Leave matching plug wire connected while checking for spark. If spark jumps tester on both plug wires, check fuel system. If spark did not jump tester on either plug wire, go to step 4).
- If spark jumped tester on only one plug wire, disconnect plug jumper wires and remove coil housing. Disconnect coil harness connector at module. Install test light between module terminal "A" and control terminal for coil which did not spark. See Figure -24.
- Crank engine and note test light. If test light blinks at both test terminals, repair faulty harness, poor connection or replace faulty coil. If test light did not blink on both terminals, repair module connections or replace faulty module.
- If spark did not occur on either plug wire in step 1), Turn ignition off. Disconnect 11-pin connector at module. Turn ignition on and connect test light between terminals "K" and "L" at harness. If test light is not on, repair open or short in module ground or power supply.
- If test light is on in step 4), install injector test light in any injector. Connect a test light to battery voltage and repeatedly touch to IDI module terminal "H". Injector test light should flash. If test light flashes, go to step 6). If not, check injector drive circuits for open or short to voltage. If ground circuits are okay, check injector power supply. If power supply is okay, repair poor connections at ECM or replace faulty ECM.
- Connect DVOM between terminals "B" and "C" of IDI module harness connector. Place DVOM on 2-volt AC scale. Crank engine and note voltage. Voltmeter should read greater than 20mV. If voltage is correct, replace IDI module. If voltage is not correct, remove crankshaft sensor from block. Measure sensor resistance. Resistance should be 500-900 ohms. Place a flat piece of metal on tip of sensor to verify sensor is still magnetized. Inspect sensor harness. Repair or replace as necessary.
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.
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.