The Manifold Absolute Pressure (MAP) sensor is a variable capacitance sensor that operates on a 5 volt reference signal from the ECM to produce a linear analog voltage signal that indicates pressure. For the MAP sensor function diagram, see Figure
“Manifold Absolute Pressure Sensor Function Diagram”
.
Figure 1. Manifold Absolute Pressure Sensor Function Diagram
Smoke Control — The MAP signal is used to control smoke by limiting fuel quantity during acceleration until a specified boost pressure is obtained.
Dynamic Injection Timing — Optimizes injection timing for boost pressure measured.
Section 36.1.1
Fault Detection / Management
A MAP signal that is detected by the ECM to be out of range or at an incorrect value for specific conditions will cause the ECM to ignore the MAP signal and will operate the engine with the values from estimated MAP. Operate from a calculated boost pressure signal.
For MAP sensor, see Figure
“Manifold Absolute Pressure Sensor”
.
Figure 2. Manifold Absolute Pressure Sensor
Connector voltage checks are listed in Table
“Connector Voltage Checks”
. Checks are made with the sensor connector disconnected and the ignition key ON.
| Test Points | Spec | Comments |
| A to Grd | 0 – 0.25 volts | If greater than 0.25 volts, signal ground wire is shorted to VREF or battery. |
| B to Grd | 5 volts ± .5 | VREF check with key ON; if voltage not in spec, see VREF circuit. |
| C to Grd | 0 – 0.25 volts | If greater than 0.25 volts, signal ground wire is shorted to VREF or battery. |
Connector checks to chassis ground are listed in Table
“Connector Checks to Chassis Ground”
. Checks are made with the sensor connector disconnected, the positive battery cable disconnected, and the ignition key OFF.
| Test Points | Spec | Comments |
| A to Grd | < 5 Ω | Resistance to chassis ground, check with key OFF; if > 5 Ω, the harness is open. |
| B to Grd | > 1,000 Ω | Resistance less than 1,000 Ω indicates a short to ground. |
| C to Grd | > 1,000 Ω | Resistance less than 1,000 Ω indicates a short to ground. |
Harness resistance checks are listed in Table
“Harness Resistance Checks”
. Checks are made with the breakout box installed on the engine harness only.
| Test Points | Spec | Comments |
| No. 19 to A | < 5 Ω | Resistance from sensor connector to 60-pin connector – Signal ground. |
| No. 40 to B | < 5 Ω | Resistance from sensor connector to 60-pin connector – VREF. |
| No. 30 to C | < 5 Ω | Resistance from sensor connector to 60-pin connector – MAP signal. |
Operational voltage checks are listed in Table
“Operational Voltage Checks”
.
| Test Points
(+) No. 30 to (-) No. 19 |
Operational Voltage Checks
(Breakout box installed in line with ECM) |
||
| Voltage | PSI | kPa | Comments |
| 0.039 v | N/A | N/A | Out of range low limit. |
| 0.92 v | 0 | 0 | Voltage with key ON, engine OFF. Atmospheric pressure dependent on altitude and barometric pressure. |
| 1.73 v | 8.0 | 56 | |
| 2.72 v | 18.0 | 124 | |
Fault code descriptions are listed in Table
“Fault Code Descriptions”
.
| Circuit Faults | Descriptions |
| 121 | Signal voltage was greater than 4.9 volts for more than 0.1 seconds. |
| 122 | Signal voltage was less than 0.039 volts for more than 0.1 seconds. |
| System Faults | Descriptions |
| 123 | Detected high boost (above 16.7 psi / 115 kPa) signal at low idle. |
Section 36.1.2
Function
The engine control system includes a Manifold Absolute Pressure (MAP) sensor. The ECM measures the signal from the MAP sensor to determine intake manifold (Boost) pressure. From this information, the ECM can optimize control of fuel rate and injection timing for all engine operating conditions.
Section 36.1.3
Operation
The MAP sensor is a variable capacitance sensor located on the intake manifold that produces a linear analog voltage signal output. The MAP sensor is supplied 5 volts from ECM pin 19 to terminal A of the sensor. A return circuit (ground) is supplied from ECM pin 40 to terminal B of the sensor. Pressure applied to the MAP sensor changes the capacitance of the sensor that varies the signal voltage sent to the ECM. As boost pressure increases, the voltage signal increases.
Section 36.1.4
ECM Diagnostics
The ECM monitors the MAP sensor output signal for expected values. If the ECM detects the MAP signal is greater than or less than the desired value, the ECM will set a fault code.
If an active MAP sensor fault code is set, the ECM will ignore the MAP signal. It will operate the engine using programmed default values. Active faults for the MAP sensor will cause the ECM to illuminate the Engine Warning light. These faults can be retrieved using the Self Test Input diagnostic switch located on the vehicle dash or the EST (Electronic Service Tool). If the ignition key is turned off, the fault code will be stored as an Inactive code.
Section 36.1.5
Flash Codes
The following flash codes are possible when troubleshooting the MAP:
Section 36.1.5.1
Flash Code 121
ATA Code PID 102 FMI 8
MAP signal out of range HIGH.
Flash Code 121 will be set if the ECM detects a MAP signal voltage greater than 4.9 volts for more than 0.1 seconds.
If Flash Code 121 is active, the ECM will ignore the MAP signal and operate the engine using programmed default values. The ECM will illuminate the Engine Warning light when this code is active.
Section 36.1.5.2
Flash Code 122
ATA Code PID 102 FMI 11
MAP signal is out of range LOW.
Flash Code 122 will be set if the ECM detects a MAP signal voltage less than .039 volts for more than 0.1 seconds.
When code 122 is active, the ECM will ignore the MAP signal and operate the engine using programmed default values. The ECM will illuminate the Engine Warning light when this code is set.
Possible causes: A defective MAP sensor or MAP sensor signal circuits may be open or shorted to ground.
Section 36.1.5.3
Flash Code 123
ATA Code PID 102 FMI 2
MAP signal above specified level at low idle.
Flash Code 123 is set when the MAP signal is greater than 16.7 psi (115 kPa) Absolute at low idle.
When code 123 is active, the ECM will ignore the MAP signal and operate the engine using programmed default values. The ECM will illuminate the Engine Warning light when this code is set.
Possible causes: Restricted or plugged sensor inlet or a defective MAP sensor.
| Series 40E Troubleshooting Manual – 6SE241 |
| Generated on 10-13-2008 |