Test DA - Adjustments Vane Air Temperature Sensor

To prevent replacement of good components, ensure that the following conditions are met:

• Test not performed in unusually cold or hot ambient temperature conditions.
• Ambient temperature must be greater than 50°F (10°C) for this test.
• Inspect all wiring, harness, connectors and components for evidence of overheating, insulation damage, looseness, shorting or other damage. If none of the above mentioned is present, proceed to test step 1).

1. VAT Resistance Check: With ignition off, install breakout box and unplug ECA. Using DVOM on 10K scale, measure resistance between pins No. 25 and 40. If resistance is not within specification, proceed to step 5). If resistance is within specification, proceed to next step.
   TYPICAL VANE AIR TEMP. (VAT) SENSOR RESISTANCE
   
   

   Ambient Temperature: °F (°C)	Ohms Between Test Pins No. 25 & 46
   32 (0)	5800
   65 (18)	2700
   185 (85)	300
   220 (104)	180
   240 (116)	125

2. VAT Voltage Check: Install breakout box. Using DVOM on 10-volt scale, turn ignition on and measure voltage between pins No. 25 and 40. At 68°F (30°C), voltage reading should be 2.4 volts. Measure voltage between pins No. 46 and 44. At 68°F (30°C), voltage reading should be zero. If all readings are within specification, replace ECA. If all readings are not within specification, proceed to next step.
3. Short Between VAT & ECA Check: Turn ignition off and disconnect battery negative terminal. Install breakout box and unplug ECA. With DVOM on 200-ohm scale, measure resistance between the following pins:
   • No. 25 and No. 1.
   • No. 25 and No. 37.
   • No. 25 and No. 40 (ground).
   • No. 46 and No. 1.
   • No. 46 and No. 37.
   If any of the resistances are less than 10,000 ohms, repair wire(s) in question. If all resistances are 10,000 ohms or more, reconnect battery and proceed to next step.
4. Signal Return Check: With ignition off and ECA unplugged, install breakout box. Using DVOM on 200-ohm scale, measure resistance between pins No. 46 and 40 (ground), and pin No. 40 (ground) and chassis ground. If resistance is less than 5 ohms, replace ECA. If resistance is 5 ohms or greater, repair open wire(s) in question.
5. Opens Between ECA & VAT: With ignition off and ECA unplugged, install breakout box. Using DVOM on 200-ohm scale, measure resistance between pin No. 25 and pin No. 46 (VAF meter Brown/Yellow wire), and VAF meter Blue/Yellow wire. If resistance is 5 ohms or more, repair wire(s) in question. If resistance is less than 5 ohms, reconnect ECA and proceed to next step.
6. VAF Sensor Resistance Check: With ignition off, unplug VAF connector. Using DVOM on 10-k/ohm scale, measure resistance between VAF meter terminals (Brown/Yellow and Yellow/Green wires, and Brown/Yellow and Blue/Yellow wires). If resistance is 2000-2500 ohms, repair short in Brown/Yellow wire from VAF to ECA. If resistance is not within specification, replace VAF meter.

Fig 1: VAT Sensor Circuit