Dodge Dakota (R1). Manual — part 42
Symptom:
*INCORRECT TEMP READING BEYOND +/-5
POSSIBLE CAUSES
*AMBIENT TEMPERATURE SENSOR
*AMBIENT TEMPERATURE SENSOR GROUND CIRCUIT OPEN
*AMBIENT TEMPERATURE SENSOR SIGNAL SHORT TO GROUND
*AMBIENT TEMPERATURE SENSOR SIGNAL CIRCUIT OPEN
*C0MPASS/MINI-TRIP COMPUTER
TEST
ACTION
APPLICABILITY
1
NOTE: Ensure that the CMTC is communicating on the PCI Bus before
proceeding with this test.
NOTE: Diagnose any PCM or HVAC DTCs before proceeding with this test.
The Ambient Temperature Sensor is hard-wired to the HVAC control head.
Ambient temperature information is transmitted to the CMTC on the PCI
Bus.
Turn the ignition off.
Disconnect the Ambient Temperature Sensor harness connector.
NOTE: To ensure accurate diagnosis of the CMTC temperature display, refer
to the following statements.
Ensure the CMTC display is in the desired mode of either Celsius or Farenheit.
The temperature display is updated based on time and vehicle speed.
At higher speeds, the temperature display is updated more frequently than at lower
speeds.
To ensure accurate temp display, vehicle should be test driven at speeds which permit
sufficient air flow over the Ambient Temperature Sensor.
This will prevent the Sensor from experiencing a
9hot soak9 condition which can
result in temperature displays higher than the actual ambient temperature.
Measure the resistance of the Ambient Temperature Sensor using the following
values:
0°C (32°F) Sensor resistance = 29.33 - 35.99 Kilohms.
10°C (50°F) Sensor resistance = 17.99 - 21.81 Kilohms
20°C (68°F) Sensor resistance = 11.37 - 13.61 Kilohms
25°C (77°F) Sensor resistance = 9.12 - 10.88 Kilohms
30°C (86°F) Sensor resistance = 7.37 - 8.75 Kilohms
40°C (104°F) Sensor resistance = 4.90 - 5.75 Kilohms
50°C (122°F) Sensor resistance = 3.33 - 3.88 Kilohms
Does the resistance measure between the min/max specifications for the current
ambient temperature?
All
Yes
→
No
→
Replace the Ambient Temperature Sensor.
Perform BODY VERIFICATION TEST - VER 1.
165
COMPASS/MINI-TRIP COMPUTER
TEST
ACTION
APPLICABILITY
2
Turn the ignition off, wait one minute.
Disconnect the Ambient Temperature Sensor harness connector.
Measure the resistance of the Sensor ground circuit to a known good ground.
Is the resistance below 5.0 ohms?
All
Yes
→
No
→
Repair the open in the Ambient Temperature Sensor ground
circuit.
Perform BODY VERIFICATION TEST - VER 1.
3
Turn the ignition off.
Disconnect the Ambient Temperature Sensor harness connector.
Measure the Ambient Temperature Sensor Signal circuit to ground.
Is the resistance below 5.0 ohms?
All
Yes
→
Repair the short to ground in the Ambient Temperature Sensor
Signal circuit.
Perform BODY VERIFICATION TEST - VER 1.
No
→
4
Turn the ignition off.
Disconnect the appropriate A/C-Heater Control harness connector(s).
Disconnect the Ambient Temperature Sensor harness connector.
Measure the resistance of the Ambient Temperature Sensor Signal circuit.
Is the resistance below 5.0 ohms?
All
Yes
→
Replace and program the Compass/Mini-Trip Computer in accor-
dance with the Service Information.
Perform BODY VERIFICATION TEST - VER 1.
No
→
Repair the open in the Ambient Temperature Sensor Signal
circuit.
Perform BODY VERIFICATION TEST - VER 1.
166
COMPASS/MINI-TRIP COMPUTER
*INCORRECT TEMP READING BEYOND +/-5 —
Continued
Symptom:
*REPAIRING CMTC DISPLAYS DOUBLE DASH ( - - ) IN TEMP
DISPLAY
POSSIBLE CAUSES
*NO RESPONSE - PCI BUS HVAC
*CMTC BUS MESSAGE FAILURE
*COMPASS MINI-TRIP COMPUTER
*AMBIENT TEMPERATURE SENSOR
*AMBIENT TEMPERATURE SENSOR SIGNAL CIRCUIT SHORT TO SENSOR GROUND CIRCUIT
*AMBIENT TEMPERATURE SENSOR SIGNAL CIRCUIT SHORT TO GROUND
*AMBIENT TEMPERATURE SENSOR SIGNAL CIRCUIT OPEN
*AMBIENT TEMPERATURE SENSOR GROUND CIRCUIT OPEN
*A/C - HEATER CONTROL
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
With the DRBIII
t, select System Monitors, J1850 Module Scan.
Does the DRBIII
t display HVAC on the BUS?
All
Yes
→
No
→
Refer to the COMMUNICATIONS category and perform the
appropriate symptom.
2
Turn the ignition on.
With the DRBIII
t, select Body, Compass Mini-Trip, System Tests, then Auto Self
Test.
Does the DRBIII
t display TEST FAILED: Bus Message Failure?
All
Yes
→
Refer to the COMMUNICATIONS category and perform the
appropriate symptom.
No
→
3
Turn the ignition on.
With the DRBIII
t, select Body, Compass Mini-Trip, System Tests, then Auto Self
Test.
Does the DRBIII
t display TEST FAILED: Internal EVIC Failure?
All
Yes
→
Replace the Compass Mini-Trip Computer in accordance with the
Service Information.
Perform BODY VERIFICATION TEST - VER 1.
No
→
167
COMPASS/MINI-TRIP COMPUTER
TEST
ACTION
APPLICABILITY
4
Turn the ignition off.
Disconnect the Ambient Temperature Sensor harness connector.
Measure the resistance of the Ambient Temperature Sensor using the following
values:
0°C (32°F) Sensor Resistance = 29.33 - 35.99 Kilohms
10°C (50°F) Sensor Resistance = 17.99 - 21.81 Kilohms
20°C (68°F) Sensor Resistance = 11.37 - 13.61 Kilohms
25°C (77°F) Sensor Resistance = 9.12 - 10.88 Kilohms
30°C (86°F) Sensor Resistance = 7.37 - 8.75 Kilohms
40°C (104°F) Sensor Resistance = 4.90 - 5.75 Kilohms
50°C (122°F) Sensor Resistance = 3.33 - 3.88 Kilohms
Does the Ambient Temperature Sensor measure within specifications?
All
Yes
→
No
→
Replace the Ambient Temperature Sensor in accordance with the
Service Information.
Perform BODY VERIFICATION TEST - VER 1.
5
Turn the ignition off.
Disconnect the Ambient Temperature Sensor harness connector.
Disconnect the appropriate A/C - Heater Control harness connector(s).
Measure the resistance of the Ambient Temperature Sensor Signal to the Sensor
Ground circuit.
Does the resistance measure less than 5.0 ohms?
All
Yes
→
Repair the Ambient Temperature Sensor Signal circuit shorted to
the Sensor Ground circuit.
Perform BODY VERIFICATION TEST - VER 1.
No
→
6
Turn the ignition off.
Disconnect the Ambient Temperature Sensor harness connector.
Disconnect the appropriate A/C - Heater Control harness connector(s).
Measure the resistance of the Ambient Temperature Sensor Signal circuit to ground.
Does the resistance measure less than 5.0 ohms?
All
Yes
→
Repair the short to ground in the Ambient Temperature Sensor
Signal circuit.
Perform BODY VERIFICATION TEST - VER 1.
No
→
7
Turn the ignition off.
Disconnect the Ambient Temperature Sensor harness connector.
Disconnect the appropriate A/C - Heater harness connector(s).
Measure the resistance of the Ambient Temperature Sensor Signal circuit.
Does the resistance measure less than 5.0 ohms?
All
Yes
→
No
→
Repair the open in the Ambient Temperature Sensor Signal
circuit.
Perform BODY VERIFICATION TEST - VER 1.
168
COMPASS/MINI-TRIP COMPUTER
*REPAIRING CMTC DISPLAYS DOUBLE DASH ( - - ) IN TEMP DISPLAY
—
Continued
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