96 computer help

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Ropolis

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back story:

I am in the process of swapping bodies on my bronco. i am going from an 81 body which already had a 96 efi motor in it, to a 93 body. i am having a problem with my 96 computer sending the proper voltage to the mass air flow sensor. currently the engine will start run for a second and then die. i figured out that mass air flow sensor was the problem when i jumpered the supply voltage for the MAF(5 volts) from the TPS sensor. then i measured the MAF sensor supply voltage coming from the computer and it was also 5 volts. however when the connector is plugged into the MAF the supply voltage from the computer goes to less than 1 volt.

Question:

Why is the voltage from the computer dropping from 5 to less than 1 when the connector is plugged into the MAF? I am guessing that i have a loose connection somewhere but where i am not sure? could it be ground, power, or a pin on the computer?

Thank you for any help!

Zach

 

Seabronc

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How about a bad MAF?

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Ropolis

Ropolis

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i thought about the MAF being bad but it runs fine when it gets a proper 5 volts.

 

miesk5

96 Bronco 5.0
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yo,

Did you get it checked for codes for free yet?

Post any Code(S) found here

=================================

Mass Air Flow Sensor to PCM in PCM Connector Pin-Out Diagram with Circuit Functions in a 96 5.0 and 5.8 (Scroll Down) from 1996 F-150, 250, 350 (4x4), and Bronco Vehicles Workshop Manual

Source: by Ford

F-Series 5.0L and 5.8L Under 8500 Lb. GVW, and All Bronco

96PCMConnectorPinOut5.05.8.gif

Pin Number Circuit Circuit Function

1 315 (P/O) PCM to Transmission Shift Solenoid No. 2

2 658 (P/LG) PCM to Check Engine Indicator Lamp

3 � Not Used

4 � Not Used

5 � Not Used

6 651 (BK/Y) Dedicated Ground

7 � Not Used

8 � Not Used

9 � Not Used

10 � Not Used

11 � Not Used

12 � Not Used

13 107 (P) PCM Flash EEPROM Power Supply

14 784 (LB/BK) 4x4 Low Range Switch to PCM Indicator Lamp

15 915 (PK/LB) J1850 Bus Negative/Data Negative (Return) to PCM

16 914 (T/O) J1850 Bus Positive/Data Positive

17 � Not Used

18 � Not Used

19 � Not Used

20 � Not Used

21 � Not Used

22 � Not Used

23 259 (O/R) Dedicated Ground to TFI Module

24 570 (BK/W) Dedicated Ground � PCM

25 875 (BK/LB) Ground Logic Module

26 � Not Used

27 237 (O/Y) PCM to Transmission Shift Solenoid No. 1

28 � Not Used

29 224 (T/W) Transmission Overdrive Cancel Switch to PCM

30 � Not Used

31 � Not Used

32 � Not Used

33 676 (PK/O) Vehicle Speed Sensor � Negative (Return) to PCM

34 � Not Used

35 392 (P/LG) Heated Exhaust Gas Oxygen Sensor No. 3 to PCM

36 968 (T/LB) Mass Airflow Return

37 923 (O/BK) Transmission Oil Temperature to PCM

38 354 (LG/R) Engine Coolant Temperature Sensor to PCM

39 743 (GY) Air Charge Temperature Sensor to PCM

40 238 (DG/Y) Fuel Pump Monitor to PCM/Fuel Pump Relay to Safety Switch

41 198 (DG/O) A/C Pressure Switch to Control Relay

42 � Not Used

43 � Not Used

44 200 (BR) PCM to Air Management No. 2 (Was TAD)

45 � Not Used

46 � Not Used

47 360 (BR/PK) PCM to Electronic Vacuum Regulator � Constant Current

48 382 (Y/BK) PCM to Test Connector No. 2

49 395 (GY/O) Profile Ignition Pickup to PCM

50 929 (PK) PCM to Spark Angle Pulse Width/Spark Output

51 570 (BK/W) Dedicated Ground � PCM

52 � Not Used

53 924 (BR/O) PCM to Transmission Coast Clutch Solenoid

54 480 (P/Y) PCM to Transmission Converter Clutch Control

55 37 (Y) Battery to Load

56 191 (LG/BK) PCM Top Vapor Management Valve � Constant Current

57 310 (Y/R) Knock Sensor No. 1 to PCM

58 679 (GY/BK) Vehicle Speed Sensor � Positive to PCM

59 917 (DG/LG) Misfire Detection Sensor � Feed

60 74 (GY/LB) Heated Exhaust Gas Oxygen Sensor No. 1 to PCM

61 � Not Used

62 � Not Used

63 � Not Used

64 199 (LB/Y) Manual Lever Position Sensor to PCM

65 352 (BR/LG) Delta Exhaust Pressure Transducer to PCM

66 � Not Used

67 � Not Used

68 � Not Used

69 � Not Used

70 190 (W/O) PCM to Air Management No. 1 (Was TAB)

71 361 ® Power Output from PCM Relay

72 561 (T/R) PCM to Fuel Injector No. 7 Cylinder

73 559 (T/BK) PCM to Fuel Injector No. 5 Cylinder

74 557 (W) PCM to Fuel Injector No. 3 Cylinder

75 555 (T) PCM to Fuel Injector No. 1 Cylinder or Bank No. 1

76 570 (BK/W) Dedicated Ground � PCM

77 570 (BK/W) Dedicated Ground � PCM

78 � Not Used

79 911 (W/LG) PCM to Output Circuit Indicator Lamp/Overdrive Cancel Indicator

80 926 (LG/O) PCM to Fuel Pump Relay Control

81 925 (W/Y) PCM to Electronic Pressure Control No. 1

82 � Not Used

83 264 (W/LB) PCM to Idle Speed Control Motor No. 1

84 136 (DB/Y) Output Shaft Speed to PCM

85 � Not Used

86 � Not Used

87 94 (R/BK) Heated Exhaust Gas Oxygen Sensor No. 2 to PCM

88 967 (LB/R) Mass Air Flow Sensor to PCM

89 355 (GY/W) Throttle Position Sensor to PCM/Diesel Fuel Injector Pump Lever Sensor

90 351 (BR/W) Power to Engine Sensors

91 359 (GY/R) Sensor Signal Return

92 511 (LG) Stoplamp (Brake On/Off) Switch to Stoplamps

93 387 (R/W) HEGO Sensor Heater Voltage Monitor No. 1 to PCM

94 388 (Y/LB) HEGO Sensor Heater Voltage Monitor No. 2 to PCM

95 389 (W/BK) HEGO Sensor Heater Voltage Monitor No. 3 to PCM

96 � Not Used

97 361 ® Power Output from PCM Relay

98 562 (LB) PCM to Fuel Injector No. 8 Cylinder

99 560 (LG/O) PCM to Fuel Injector No. 6 Cylinder

100 558 (BR/LB) PCM to Fuel Injector No. 4 Cylinder

101 556 (W) PCM to Fuel Injector No. 2 Cylinder or Bank No. 2

102 � Not Used

103 570 (BK/W) Dedicated Ground � PCM

104 � Not Used

========

MAF Connector Pin-Out Diagrams, pic & Air Flow Depiction

Source: by Ryan M (Fireguy50) at http://fordfuelinjection.com/index.php?p=26

maf04.gif


============================

Ford Hot Wire MAF Sensor

..the MAF sensor sends either a variable voltage to the computer. The computer is programmed to accept this information when the vehicle is running in any mode. For example, idle rpm will send a low voltage and a high revving engine will send a high voltage to the computer along a specific wire (the MAF signal wire). If the signal is not present when it should be and within a programmed parameter, say high voltage at high throttle opening, the computer will set a code.

So, there are several things to consider whenever there is a code which points to the MAF sensor as the problem:

Derive the code(s) by the manufacturer's recommended method.

Look up the code(s) in a service manual

Read the explanation(s) carefully!

A code that indicates an out of range signal is often an indication that another sensor, like the throttle position sensor is contradicting the MAF signal. The cause might be the other sensor or signal being out of adjustment or faulty.

A code that indicates a low MAF signal may be set by various problems.

These include the following:

A bad MAF sensor (internal fault)

Any wire on the MAF sensor circuit including:

The 12 volt feed wire which connects the MAF to the battery through the ignition switch

The MAF ground wire

The output wire

The MAF or computer connectors

The computer (EEC V)

========================

I have more MAF info in my site under Fuel

EFI

MAF

such as:

MAF Servicing TSB 96-22-5 for 94-96 Source: by Ford via miesk5 at cc

an excerpt;

".... On a fully warmed up engine, look at MAF voltage at idle, in Neutral, A/C off (MAF V PID). If it's 30% greater than the nominal MAF V voltage listed in the Powertrain Control/Emissions Diagnosis (PC/ED) Diagnostic Value Reference Charts for your vehicle, or greater than 1.1 volts as a rough guide, the MAF sensor is over-estimating air flow at idle.

4. If at least two of the previous three steps are true, proceed to disconnect the MAF sensor connector. This puts the vehicle into Failure Mode and Effects Management (FMEM). In FMEM mode, air flow is inferred by using rpm and throttle position instead of reading the MAF sensor. (In addition, the BARO value is reset to a base/unlearned value.) If the lean driveability symptoms go away, the MAF sensor is probably contaminated and should be replaced. If the lean driveability symptoms do not go away, go to the PC/ED Service Manual for the appropriate diagnostics.

NOTE:

DUE TO INCREASINGLY STRINGENT EMISSION/OBDII REQUIREMENTS, IT IS POSSIBLE FOR SOME VEHICLES WITH MAF SENSOR CONTAMINATION TO SET FUEL SYSTEM DTCs AND ILLUMINATE THE MIL WITH NO DRIVEABILITY CONCERNS. DISCONNECTING THE MAF ON THESE VEHICLES WILL, THEREFORE, PRODUCE NO IMPROVEMENTS IN DRIVEABILITY. IN THESE CASES, IF THE BARO, LONGFT1, LONGFT2, AND MAF V PIDs INDICATE THAT THE MAF IS CONTAMINATED, PROCEED TO REPLACE THE MAF SENSOR.

After replacing the MAF sensor, disconnect the vehicle battery (5 minutes, minimum) to reset KAM, or on newer vehicles, use the "KAM Reset" feature on the New Generation Star (NGS) Tester and verify that the lean driveability symptoms are gone..."

 
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