2010 Cadillac Truck SRX AWD V6-3.0L Page 1123
* Any damaged components
* Loose or improper installation
* An air flow restriction
* Any vacuum leak
* Improperly routed vacuum hoses
* In cold climates, inspect for any snow or ice buildup
* Verify that restrictions do not exist in the MAP sensor port or vacuum source.
2. Ignition OFF for 90 s, disconnect the harness connector at the B74 MAP sensor.
3. Ignition OFF, test for less than 5 ohm between the low reference circuit terminal 2 and ground.
瀚慖f greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20
ECM.
4. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground.
瀚慖f less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal,
replace the K20 ECM.
瀚慖f greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
5. Verify the scan tool MAP Sensor parameter is less than 1 kPa (0.2 psi).
瀚慖f greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the K20 ECM.
6. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the 5 V reference circuit terminal 1. Verify the scan tool MAP
Sensor parameter is greater than 127 kPa (18.4 psi).
瀚慖f less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace
the K20 ECM.
7. If the circuits test normal, test or replace the B74 MAP sensor.
Component Testing
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 Signal Test
1. Using the following steps and referencing the table below will determine if the MAP sensor is skewed.
2. Ignition ON, engine OFF, observe the MAP Sensor scan tool parameter.
3. Use the observed MAP Sensor scan tool parameter that is closest to a value that is indicated in the first column.
THEN
4. Using the J 23738-A - Mityvac or the J 35555 - Metal Mityvac to apply 5 in Hg of vacuum to the B74 MAP sensor, the parameter in the first
column should decrease by 17 kPa (2.5 psi). The acceptable range is indicated in the second column.
5. Using the J 23738-A - Mityvac or the J 35555 - Metal Mityvac to apply 10 in Hg of vacuum to the B74 MAP sensor, the parameter in the
first column should decrease by 34 kPa (4.9 psi). The acceptable range is indicated in the third column.
Erratic Signal Test
1. Ignition OFF, remove the B74 MAP sensor.
2. Install a 3 A fused jumper wire between the 5 V reference circuit terminal 1 and the corresponding terminal of the B74 MAP sensor.
3. Install a jumper wire between the low reference circuit terminal 2 of the B74 MAP sensor and ground.
4. Install a jumper wire at terminal 3 of the B74 MAP sensor.
5. Connect a DMM between the jumper wire from terminal 3 of the B74 MAP sensor and ground.
6. Ignition ON, with the J 23738-A - Mityvac or J 35555 - Metal Mityvac , slowly apply vacuum to the sensor while observing the voltage on
the DMM. The voltage should vary between 0-5.2 V, without any spikes or dropouts.
瀚慖f the voltage reading is erratic, replace the B74 MAP sensor.
