Circuit Description
The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure (vacuum). A 5 volt reference is applied to the sensor on the 5 volt reference circuit. A variable resistor moves in relation to the manifold pressure and a voltage signal is sent back to the VCM on the MAP signal circuit. This voltage signal varies from 1.0-1.5 volts at closed throttle to 4.0-4.5 volts at wide open throttle (low vacuum). The VCM utilizes the MAP signal and throttle position in order to determine the correct amount of fuel delivered to the engine. This DTC is a type A DTC.
Conditions for Setting the DTC
The following conditions will set the DTC:
| • | No TP sensor DTCs are set |
| • | Throttle Position is no more than 0.4% when engine speed is no more than 1200 RPM |
| • | Or the Throttle Position is no more than 19.9% when engine speed is greater than 1200 RPM |
| • | MAP is greater than or equal to 4.34 volts |
Action Taken When the DTC Sets
The VCM turns ON the MIL when 1 failure has occurred. The VCM substitutes a calculated value for the MAP sensor value so an acceptable driving condition is maintained.
Conditions for Clearing the MIL/DTC
The VCM turns OFF the MIL after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (the coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle) or the scan tool clearing feature has been used.
Diagnostic Aids
An intermittent ground in the MAP signal or the 5 volt reference circuit results in a DTC P1106.
With the ignition ON and the engine OFF, the manifold pressure is equal to atmospheric pressure with the signal voltage high. The VCM uses this information as an indication of the vehicle's altitude. Comparison of this reading with a known good vehicle using the same sensor is a good way to check accuracy of a suspect sensor. Readings should be the same ±0.4 volts.
Refer to Intermittent Conditions .
Important: The electrical connector must remain securley fastened.
Important: After removing the MAP sensor from the intake manifold, replace the MAP sensor to intake manifold seal.
Remove the MAP sensor. Twist sensor by hand (only) to check for intermittent connections. Output changes greater than 0.1 volt indicates a bad connector or connection. If OK, replace sensor.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Important: Be sure to use the same diagnostic equipment for all measurements.
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This step checks for a short to voltage on the 5V reference circuit.
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This step checks the integrity of the MAP sensor ground circuit.
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VCM pins GR12 and GR 27 are spliced together inside the VCM. This step isolates the two pins from one another.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing DTCs, use the scan tool in order to record freeze frame and the failure records for reference because the Clear Info function will lose the data. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 |
Does the scan tool display a voltage less than the specified value? | 4.0 V | ||
3 |
Does the scan tool display a voltage less than the specified value? | 1.0 V | ||
4 | The DTC is intermittent. If no additional DTCs are stored, refer to the Diagnostic Aids. If additional DTCs are stored, refer to those tables first. Are any additional DTCs stored? | -- | Go to The Applicable DTC Tables | -- |
With a DVM connected to ground, probe the 5V reference circuit at the MAP sensor harness connector. Is the voltage greater than the specified value? | 5.2V | |||
Probe the MAP sensor ground circuit (at the MAP sensor connector) with a test light to B+. Is the test light ON? | -- | |||
7 | Check the MAP sensor vacuum source for a restriction. Was a problem found? | -- | ||
8 | Replace the MAP sensor. Refer to MAP Sensor Replacement for the 4.3L. Is the replacement complete? | -- | -- | |
9 | Check for a short to the voltage in the MAP sensor signal circuit. Was a problem found? | -- | ||
Is the voltage greater than the specified value? | 5.2V | |||
11 |
Is the voltage greater than the specified value? | 5.2V | ||
12 | Repair the short to ground on the 5V reference circuit. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
13 | With a DVM connected to ground, measure the voltage on the VCM connector terminal GR12. Is the voltage greater than the specified value? | 5.2V | ||
14 | Repair the MAP sensor ground circuit. Refer to Wiring Repairs in Engine Electrical. Is the repair complete? | -- | -- | |
15 | Repair as necessary. Is the action complete? | -- | -- | |
16 | Replace the EGR valve. Refer to EGR Valve Replacement for the 4.3L. Is the action complete? | -- | -- | |
17 | Repair the short to voltage on the 5V reference circuit (terminal GR12). Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
18 | Replace the VCM. Important: If the VCM is faulty, reprogram the VCM. Refer to VCM Replacement/Programming . Is the action complete? | -- | -- | |
19 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
20 | Using the scan tool, select the capture info and the review info. Are any DTCs displayed which were not diagnosed? | -- | Go to The Applicable DTC Table | System OK |
