Test DF - BARO Sensor

Inspect for obstructed vacuum lines, basic engine mechanical operation, wiring, wiring harness and insulation condition, before proceeding with test procedures.

1. VREF & Signal Return Check: Install breakout box and connect ECA. Using DVOM on 20-volt scale, turn ignition on and measure voltage between the following pins:

   Vehicles built before 11/2/87.

   • No. 19 and No. 46.
   • No. 19 and No. 40.
   • No. 46 and No. 40

   Vehicles built after 11/2/87.

   • No. 26 and No. 46.
   • No. 26 and No. 40.
   • No. 46 and No. 40.
   Voltage reading should indicate 4-6 volts on all except those readings taken from pins No. 46 and 40. Voltage reading on pins No. 46 and 40 should indicate zero volts. If voltage readings are within specification, proceed to next step. If voltage reading is greater than specification, proceed to step 5). If voltage reading is less than specification, proceed to step 6).
2. Check For BARO Sensor Voltage: Connect vacuum pump to BARO sensor and install breakout box. Using DVOM on 20-volt scale, with ignition on, measure voltage between pins No. 45 and 46. With zero vacuum, reading should be 3.5-4.5 volts. At 30 in. Hg, reading should indicate zero volts. If reading is within specification, replace ECA. If reading is not within specification, proceed to next step.
3. BARO Sensor Power Check: Using DVOM on 20-volt scale and ignition turned on, measure voltage between wires indicated in BARO POWER CHECK table. If voltage is not within specification, repair appropriate wire(s) in question. If voltage is within specification, proceed to next step.
   BARO POWER CHECK (VEHICLES BUILT AFTER 11/2/87)
   
   

   Between	Voltage
   White/Black Wire & Ground	4-6
   White/Black & Blue/Yellow Wires	Zero
   Blue/Yellow Wire & Ground	Zero

   BARO POWER CHECK (VEHICLES BUILT BEFORE 11/2/87)
   
   

   Between	Voltage
   Green Wire & Ground	4-6
   Green Wire & Blue/Yellow Wires	4-6
   Blue/Yellow Wire & Ground	Zero

4. BARO Sensor Voltage Check: Connect vacuum pump to BARO sensor. Unplug BARO sensor connector. Using DVOM on 20-volt scale, turn ignition on and measure voltage between Light Green wire and ground. With zero vacuum, reading should be zero volts. At 30 in. Hg, reading should be 3.5-4.5 volts. If reading is within specification, repair open in Light Green wire from BARO sensor to ECA. If reading is not within specification, replace BARO sensor.
5. VREF Short Check: Turn ignition off and install breakout box. Unplug ECA and using DVOM on 200-k/ohm scale, measure resistance between VREF pin No. 19 and KAPWR pin No. 1, and VREF pin No. 19 and VPWR pin No. 37 on vehicles built before 11/2/87. On all others, measure resistance between VREF pin No. 26 and KAPWR pin No. 1, and VREF pin No. 26 and VPWR pin No. 37. If resistances are less than 10,000 ohms, repair short to voltage in Green wire on vehicles built before 11/2/87. On all others, repair White/Black wire. If resistances are 10,000 ohms or more, replace ECA.
6. ECA Power Check: Install breakout box. Using DVOM on 20 volt scale, with ignition on, measure voltage between pins No. 1 and 40 (ground), and pins No. 37 and 40 (ground). If reading is greater than 10 volts, proceed to next step. If reading is 10 volts or less, proceed to TEST FC  .
7. Signal Return To Ground Check: Turn ignition off and install breakout box. Plug in ECA. Using DVOM on 200-ohm scale, measure voltage between pin No. 40 and chassis ground. If resistance is less than 5 ohms, replace ECA. If resistance is 5 ohms or greater, repair open in ground (Black wire).
8. ECA Ground Check: Turn ignition off and install breakout box. Using DVOM on 200-ohm scale, measure resistance between pin No. 40 and chassis ground. If resistance is less than 5 ohms, replace ECA. If resistance is 5 ohms or greater, repair open in ground (Black wire).

Fig 1: BARO Sensor Circuit