Manifold Absolute Pressure Sensor Output Diagnosis. Chevrolet Blazer

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1996 🢒 Blazer - 2WD 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 Manifold Absolute Pressure Sensor Output Diagnosis

Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Engine Controls Components
MAP, A/C, and Fuel Tank Pressure Sensors
OBD II Symbol Description Notice

Circuit Description

The Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure which result from the engine load (intake manifold vacuum) and the RPM changes then converts these into a voltage output. The Powertrain Control Module (PCM) supplies a 5 volt reference voltage to the MAP sensor. As the manifold pressure changes, the output voltage of the sensor also changes. By monitoring the sensor output voltage, the PCM knows the manifold pressure. A lower pressure (low voltage) output voltage will be about 1.0 to 1.5 volts at idle. While high pressure (high voltage) output voltage will be about 4.5 to 4.8 volts at Wide Open Throttle (WOT). The MAP sensor is also used, under certain conditions, to measure barometric pressure, allowing the PCM to make adjustment for different altitudes. The PCM uses the MAP sensor in order to control the fuel delivery and the ignition timing.

Test Description

The numbers below refer to step numbers in the diagnostic table.

The OBD System Check prompts the technician to store the Freeze Frame Data in the scan tool. This creates an electronic copy of the freeze frame data taken when the fault occurred that can be referred to later.

Applying 34 kPa (10" Hg vacuum to the MAP sensor should cause the voltage to be 1.5 to 2.1 volts less than the voltage at Step 1. Upon applying the vacuum to the sensor, the change in the voltage should be instantaneous. A slow voltage change indicates a faulty sensor.

Check the vacuum hose to the sensor for leakage or restrictions. Do not connect other vacuum devices to the MAP sensor hose.

Move the MAP sensor electrical connector by hand (only) while watching the scan tool in order to check for an intermittent connection. The output changes greater than 0.10 volt indicate a bad connection.

Step	Action	Value(s)	Yes	No
1	Was the On-Board Diagnostic (OBD) System Check performed?	--	Go to Step 2	Go to Powertrain On Board Diagnostic (OBD) System Check
2	Install a scan tool. Check for MAP DTCs. Were any MAP DTCs set?	--	Go to the Applicable DTC Table	Go to Step 3
3	Turn ON the ignition leaving the engine OFF. View the Engine 1 screens MAP voltage. Compare this reading with the reading of a known good vehicle. Are the voltage readings between the 2 vehicles within the specified value?	±0.4 V	Go to Step 4	Go to Step 5
4	Disconnect the vacuum source to the MAP sensor. Plug the vacuum source to the MAP sensor. Connect a hand vacuum pump to the MAP sensor. Make note of the MAP sensor voltage on the scan tool. Apply the specified vacuum to the sensor. Make note of the MAP sensor voltage on the scan tool. Subtract the second voltage reading from the first voltage reading. Is the deference greater than the specified value?	34 kPa (10" Hg) 1.5 V	Go to Step 6	Go to Step 7
5	Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Is the action complete?	--	Go to Step 9	--
6	Check the MAP sensor vacuum source for leakage or for a restriction. Check that the vacuum source supplies the MAP sensor only. Was problem found?	--	Go to Step 8	Go to Step 9
7	Check the MAP sensor electrical connector terminals. Repair as necessary. Refer to Wiring Repairs in Engine Electrical. Was a repair necessary?	--	Go to Step 9	Go to Step 5
8	Repair the leakage or restriction in the MAP sensor vacuum source. Is the action complete?	--	Go to Step 9	--
9	Operate the vehicle within the conditions under which the original symptom was noted. Does the system now operate properly?	--	System OK	Go to Step 2