Component Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
You must perform the Circuit/System Testing in order to verify the integrity of the MAP sensor circuits before proceeding with the Component Testing.
Skewed Sensor Test
- Using the following steps and referencing the table below will determine if the B74 manifold absolute pressure sensor is skewed.
- Ignition ON, engine OFF, observe the MAP Sensor scan tool parameter.
- Use the observed MAP Sensor Scan Tool parameter that is closest to a value that is indicated in the first column.
THEN
- Using the J-23738-A
Vacuum Pump to apply 5 in Hg of vacuum to the B74 manifold absolute pressure sensor, the parameter in the first column should decrease by 17 kPa (2.5 psi). The acceptable range is indicated in the second column.
- If not within the acceptable range
Replace the B74 manifold absolute pressure sensor.
- If within the acceptable range
- If not within the acceptable range
- Using the J-23738-A
Vacuum Pump to apply 10 in Hg of vacuum to the B74 manifold absolute pressure sensor, the parameter in the first column should decrease by 34 kPa (5.0 psi). The acceptable range is indicated in the third column.
- If not within the acceptable range
Replace the B74 manifold absolute pressure sensor.
- If within the acceptable range
- If not within the acceptable range
- All OK.
| Ignition ON, Engine OFF, MAP Sensor Parameter | MAP Sensor Parameter With 5 Inches of Vacuum Applied | MAP Sensor Parameter With 10 Inches of Vacuum Applied |
|---|---|---|
| 100 kPa (14.5 psi) | 79-87 kPa (11.5-12.6 psi) | 62-70 kPa (9.0-10.2 psi) |
| 95 kPa (13.8 psi) | 74-82 kPa (10.7-11.9 psi) | 57-65 kPa (8.3-9.4 psi) |
| 90 kPa (13.1 psi) | 69-77 kPa (10.0-11.2 psi) | 52-60 kPa (7.5-8.7 psi) |
| 80 kPa (11.6 psi) | 59-67 kPa (8.6-9.7 psi) | 42-50 kPa (6.1-7.3 psi) |
| 70 kPa (10.2 psi) | 49-57 kPa (7.2-8.3 psi) | 32-40 kPa (4.6-5.8 psi) |
| 60 kPa (8.7 psi) | 39-47 kPa (5.7-6.9 psi) | 22-30 kPa (3.2-4.4 psi) |
Erratic Signal Test
- Ignition OFF, remove the B74 manifold absolute pressure sensor.
- Install a 3A fused jumper wire between the 5 V reference circuit terminal C or 1 and the corresponding terminal of the B74 manifold absolute pressure sensor.
- Install a jumper wire between the low reference terminal A or 2 of the B74 manifold absolute pressure sensor and ground.
- Install a jumper wire at terminal B or 3 of the B74 manifold absolute pressure sensor.
- Connect a DMM between the jumper wire from the terminal B or 3 of the B74 manifold absolute pressure sensor and ground.
- Ignition ON, with the J-23738-A
Vacuum Pump, slowly apply vacuum to the sensor while observing the voltage on the DMM. The voltage should vary between 4.9-0.2 V without any spikes or dropouts.
- If not between 4.9-0.2 V or has spikes or dropouts
Replace the B74 manifold absolute pressure sensor.
- If between 4.9-0.2 V and there are no spikes or dropouts
- If not between 4.9-0.2 V or has spikes or dropouts
- All OK.