DL: Cylinder Head Temperature (CHT) Sensor
Introduction
Introduction
1999 PCED On Board Diagnostics II |
SECTION 5: Pinpoint Tests |
DL: Cylinder Head Temperature (CHT) Sensor Introduction |
DL: Pinpoint Tests |
This Pinpoint Test is intended to diagnose the following:
On applications that do not use a ECT sensor, the CHT sensor is used to determine the engine coolant temperature in place of the ECT sensor. In this case the PCM may store both CHT and ECT Diagnostic Trouble Codes (DTCs). To cover the entire temperature range of both the CHT and ECT sensors, the PCM has a dual switching resistor circuit on the CHT input. A graph showing the temperature switching from the COLD END line to the HOT END line with increasing temperature and back with decreasing temperature is included. Note the temperature to voltage overlap zone. Within this zone it is possible to have either a COLD END or HOT END voltage at the same temperature. For example, at 90°C (194°F) the voltage could read either 0.60 volt or 3.71 volts. Refer to the table for the temperature to voltage expected values.
Voltage values were calculated for VREF = 5.0 volts. These values can vary 15 percent due to sensor and VREF variations.
CYLINDER HEAD TEMPERATURE SENSOR EXPECTED VALUES
| Temperature | CHT Sensor Values | |||
|---|---|---|---|---|
| °C | °F | COLD END | HOT END | Resistance (K ohms) |
| -40 | -40 | 4.89 | — | 965.808 |
| -30 | -22 | 4.81 | — | 513.019 |
| -20 | -4 | 4.67 | — | 283.664 |
| -10 | 14 | 4.45 | — | 162.584 |
| 0 | 32 | 4.14 | — | 96.255 |
| 10 | 50 | 3.73 | — | 59.175 |
| 20 | 68 | 3.26 | — | 37.387 |
| 30 | 86 | 2.74 | — | 24.215 |
| 40 | 104 | 2.23 | — | 16.043 |
| 50 | 122 | 1.76 | — | 10.85 |
| 60 | 140 | 1.36 | — | 7.487 |
| 70 | 158 | 1.04 | — | 5.268 |
| 80 | 176 | 0.79 | 3.99 | 3.775 |
| 85 | 185 | 0.69 | 3.86 | 3.215 |
| 90 | 194 | 0.60 | 3.71 | 2.75 |
| 95 | 203 | 0.53 | 3.56 | 2.361 |
| 100 | 212 | 0.46 | 3.41 | 2.034 |
| 110 | 230 | — | 3.07 | 1.523 |
| 120 | 248 | — | 2.74 | 1.155 |
| 130 | 266 | — | 2.41 | 0.8866 |
| 140 | 284 | — | 2.10 | 0.6891 |
| 150 | 302 | — | 1.81 | 0.5417 |
| 160 | 320 | — | 1.55 | 0.4301 |
| 170 | 338 | — | 1.33 | 0.3449 |
| 180 | 356 | — | 1.13 | 0.2791 |
| 190 | 374 | — | 0.96 | 0.2278 |
| 200 | 392 | — | 0.82 | 0.1875 |
| 210 | 410 | — | 0.70 | 0.155 |
| 220 | 428 | — | 0.60 | 0.130 |
| 230 | 446 | — | 0.51 | 0.109 |
| 240 | 464 | — | 0.44 | 0.092 |
| 250 | 482 | — | 0.35 | 0.078 |
| 260 | 500 | — | 0.33 | 0.067 |
| DL: Pinpoint Tests |