SIGNAL FUNCTIONS
The Manifold Absolute Pressure (MAP) sensor is a variable
capacitance sensor which operates on a 5 volt reference signal from
the PCM to produce a digital frequency signal that indicates
pressure.
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.
FAULT DETECTION MANAGEMENT
A MAP signal that is detected by the PCM to be out of range or at an
incorrect value for specific conditions will cause the PCM to ignore
the MAP signal and will operate the engine with the values from
estimated MAP. (Operate from a calculated boost pressure
signal.)
The NGS tool will display a fixed PID value of 14.6 PSI (100 kPA)
with a MAP signal fault present.
After removing connector always check for
damaged pins, corrosion, loose terminals, etc.
| Connector Checks to Ground (B-) |
| (Check with IPR Connector Disconnected and
Ignition key off, all accessories off) |
| Test Points |
Spec. |
Comments |
| A to Grd. |
< 5 ohms |
Resistance to chassis ground check with key off, if > than 5
ohms harness is open. |
| B to Grd. |
> 1000 ohms |
Resistance less than 1000 ohms indicates a short to ground.
- VRef. |
| B to Grd. |
> 1000 ohms |
Resistance less than 1000 ohms indicates a short to ground.
- MAP signal. |
| Connector Voltage Checks |
| (Check with sensor Connector Disconnected and
Ignition Key On) |
| Test Points |
Spec. |
Comments |
| A to Grd. |
0 - .25v |
If greater than .25 volts, signal circuit shorted to VRef or
battery. |
| B to Grd. |
5 volts ± .5 |
V Ref. check with key ON, if voltage not in spec, see V REF
circuit. |
| B to Grd. |
4.8 - 5.0 v |
Pull up voltage, if no or low voltage circuit has open or
high resistance or short to grd. |
| Harness Resistance Checks |
| (Check with breakout box installed on engine
harness only) |
| Test Points |
Spec. |
Comments |
| #91 to A |
< 5 ohms |
Resistance from sensor connector to 104 pin connector -
Signal ground |
| #90 to B |
< 5 ohms |
Resistance from sensor connector to 104 pin connector - V
Ref |
| #34 to C |
< 5 ohms |
Resistance from sensor connector to 104 pin connector - MAP
signal |
| Test Points |
Operational Voltage Checks |
| (+) #34 to (-) #91 |
(Check with breakout box installed in line with
the PCM) |
| Frequency |
PSIA |
kPAG |
MGP (PSI) |
Comments |
| 111 Hz. |
14.7 |
101 |
0 (0) |
Freq with key on, engine off. Atmospheric pressure
dependent on altitude and BARO psi. |
| 130 Hz. |
20 |
138 |
38 (5.3) |
Expected frequency values at absolute
pressures. |
| 167 Hz. |
30 |
207 |
107 (15.3) |
| 203 Hz. |
40 |
276 |
176 (25.3) |
| Diagnostic Trouble Code Description |
| Circuit Faults: |
| 0237 |
= |
Signal frequency was greater than 256 Hz. for more than 0.1
seconds. |
| 0235 |
= |
Signal frequency was less than 78 Hz. or inactive for more
than 0.10 seconds. |
| System Faults: |
| 0236 |
= |
Detected high boost signal at low idle. (Restricted
MAP line.) (Inrange Fault) |
|
