Hard Start: Sensor/System
- Check Engine Coolant Temperature (ECT) sensor for being shifted in value. Connect a scan tool and compare ECT with Intake Air Temperature (IAT) on a cold engine. The ECT and IAT should be within 5°F of each other. Check the resistance of the ECT sensor if the temperature is out of range with the IAT sensor. See TEMPERATURE VS. RESISTANCE table. If the ECT sensor resistance is not within specification, see DTC P0113: INTAKE AIR TEMPERATURE SENSOR CIRCUIT - HIGH VOLTAGE under DIAGNOSTIC TESTS in SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.1L CENTURY, GRAND PRIX & MALIBU article. On Malibu, also see DTC P0117: ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT - LOW VOLTAGE under DIAGNOSTIC TESTS in SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.1L CENTURY, GRAND PRIX & MALIBU article.
- Monitor the 24X crank sensor and Camshaft Position (CMP) sensor signal present parameters on a scan tool. If both are not responding, test the sensor feed circuit. Both sensors use a separate feed circuit but are internally connected to power. Check all CKP sensor "A" and CMP sensor circuits for intermittents. See INTERMITTENTS .
- Monitor the 3X crank sensor parameter on the scan tool. If the 3X crank sensor parameter is not responding, check the CKP sensor and circuits for intermittents. Check the Ignition Control (IC) circuit, IC timing control circuit, low resolution engine speed signal circuit and the low reference circuit for intermittents. If these circuits become open, or shorted, they may not set a DTC immediately, but are capable of causing driveability complaints. See INTERMITTENTS .
- Check the Mass Airflow (MAF) sensor for proper installation and conditions. A MAF sensor with a damaged honeycomb may cause a hard start. Check the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking, especially between the MAF sensor and the throttle body.
- Using a scan tool, test the Idle Air Control (IAC) operation. Command the engine RPM to 1500 RPM and back to the starting RPM. If the engine RPM does not change when commanded, diagnose the IAC system. See DTC P0506: IDLE SPEED LOW and DTC P0507: IDLE SPEED HIGH under DIAGNOSTIC TESTS in SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.1L CENTURY, GRAND PRIX & MALIBU article.
- Check the Exhaust Gas Recirculation (EGR) system for proper sealing/connections and operation. See EXHAUST GAS RECIRCULATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 3.1L CENTURY, GRAND PRIX & MALIBU article.
TEMPERATURE VS. RESISTANCE
| °F (°C) | Ohms |
|---|---|
| 302 (150) | 47 |
| 284 (140) | 60 |
| 266 (130) | 77 |
| 248 (120) | 100 |
| 230 (110) | 132 |
| 212 (100) | 177 |
| 194 (90) | 241 |
| 176 (80) | 332 |
| 158 (70) | 467 |
| 140 (60) | 667 |
| 122 (50) | 973 |
| 113 (45) | 1188 |
| 104 (40) | 1459 |
| 95 (35) | 1802 |
| 86 (30) | 2238 |
| 77 (25) | 2796 |
| 68 (20) | 3520 |
| 59 (15) | 4450 |
| 50 (10) | 5670 |
| 41 (5) | 7280 |
| 32 (0) | 9420 |
| 23 (-5) | 12,300 |
| 14 (-10) | 16,180 |
| 5 (-15) | 21,450 |
| -4 (-20) | 28,680 |
| -22 (-30) | 52,700 |
| -40 (-40) | 100,700 |