ENGINE AND ENGINE SYSTEMS 5540F/YB5515 SERVICE MANUAL
6-18 Published 10-21-2010, Control# 198-04
Code 15: The engine coolant reads too low. This may occur if the temperature is below 30° F (-1° C), or if the coolant tem-
perature sensor is unplugged.
To verify coolant temperature wiring:
1. Disconnect the coolant temperature sensor (CTS) and measure the resistance of the coolant temperature
sensor. This will vary depending on the sensor’s temperature. The resistance should be within 5% of that
listed below. If the sensor differs, replace the sensor.
2. Turn ignition power ON.
2.1 Measure the voltage between the CTS sensor pin A (WHT/BK) and ground. This should read near 5
volts. If it does not proceed to step 2.1.1.
2.1.1 Turn off the ignition power and disconnect the ECM.
2.1.2 Measure the resistance from ECM pin 9 to CTS pin A. It should read less then 1 ohm. If it does
not repair the wire.
2.1.3 Measure the resistance from the ECM connector pin 10 to sensor pin B (BK/YL). It should read
less then 1 ohm. If it does not, repair the wire.
2.2 If no sensor or wiring problems are found, replace the ECM.
Code 21: The throttle position sensor (TPS) is reading incorrectly. Make sure the throttle position sensor is plugged in.
To verify the throttle position sensor and wiring:
1. Disconnect the throttle position sensor from the harness.
1.1 Measure the resistance between TPS pins A and B. This should read 2.5 - 7.5 ohms. If it is outside this
range, replace the sensor.
1.2 Measure the resistance from pin A to pin C while slowly, manually move the throttle plate. The resis-
tance should increase smoothly without dips or spikes. If it is not smooth replace the sensor.
2. Turn the ignition power ON. Measure voltage from harness to TPS connector pins A (-) and B (+). This
should measure 4.75 to 5.25 volts. If not proceed with step 2-1.
2.1 Perform the following measurements:
2.2 Turn the ignition power OFF. Disconnect the ECM from the wiring harness. Disconnect the MAP sensor
CTS/IAT Resistance
Degrees F (C) CTS Resistance (Ohms) IAT Resistance (Ohms)
-22 (-30) 52594 51791
5 (-20) 21371 21044
32 (0) 9399 12073
68 (20) 3511 3457
77 (25) 2795 2752
86 (3) 2240 2205
95 (35) 1806 1778
104 (40) 1465 1443
140 (60) 671 660
167 (75) 395 398
176 (80) 334 329
194 (90) 242 238
203 (95) 207 204
212 (100) 178 175
248 (120) 100.9 99
Reference Only
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