Code 51 I have a 95 ford f150 with 5.0 that has a flashing air bag light that gave me a code of 51, which by code book for ford means 'ECT sensor". I also, Have had times of the A/C going out to floor panel when i press down on gas pedal to pass someone. I checked vacuum and found no problems....It"s a guess at this point for me...Thanx for any help.

Code 21 is for the passenger side air bag circuit. Could be the air bag, the seat sensor, or a wiring problem.

Has the vehicle been in a crash or minor accident recently? Have you installed any amps or anything under the seats? Are seatbelt tensioners working properly? These are typical issues.
Here is a list of airbag codes:
Air Bag Fault Code Table
AIR BAG DIAGNOSTIC MONITOR FAULT CODE PRIORITY TABLE
Priority Code Component/Fault Description
Highest -- No Air Bag Lamp - Inoperative Lamp Circuit or No Ignition Voltage to Diagnostic Monitor
' -- Continuous Air Bag Lamp - Diagnostic Monitor Disconnected or Inoperative
' 12 Low Battery Voltage
' 13 Air Bag Circuit or Crash Sensor Circuit - Shorted to Ground
' 21 Safing Sensor - Not Mounted on Vehicle Properly
' 22 Safing Sensor Output Circuit - Shorted to Battery Voltage
' 23 Safing Sensor Input Feed/Return Circuit Open
' 24 Open in Circuit 944B or Low Resistance in Crash Sensor(s)
' 32 Driver Side Air Bag/Safing Sensor Circuit - High Resistance or Open
' 33 Pin 7 Not Grounded at Diagnostic Monitor
' 34 Driver Side Air Bag/Safing Sensor Circuit - Low Resistance or Shorted
' 35 Low Resistance Across Pins 8 and 9 at Diagnostic Monitor
' 41 Crash Sensor Circuit - High Resistance or Open
' 44 RH Crash Sensor - Not Mounted to Vehicle Properly
' 45 Center Radiator Crash Sensor - Not Mounted to Vehicle Properly
' 46 LH Crash Sensor - Not Mounted to Vehicle Properly
' 51 Diagnostic Monitor Internal Thermal Fuse - Blown and Short to Ground No Longer Exists
' 52 Backup Power Supply - Voltage Boost Fault
' 53 Internal Diagnostic Monitor Fault
Lowest -- Rapid Continuous Flashing of Air Bag Lamp - All Crash Sensors Disconnected

first things first is you need to know what code(s) have set

The system readiness indicator light (AIR BAG warning light) is used in diagnosing malfunctions or faults in the air bag system. A fault code will be displayed when the ignition switch is in the RUN position and the diagnostic monitor detects a system fault. Certain faults may not be displayed until approximately 30 seconds after ignition switch has been turned to RUN position. This is the amount of time required for diagnostic monitor to test and verify all system faults.
AIR BAG warning light flashes a series of 2-digit fault codes. For example, a fault Code 32 will be displayed in the following manner: flash flash flash, one-second pause, flash flash, 3-second pause, then the cycle would repeat.

Once you have the code(s) post them here

I think you might have a bad air bag module or sensor that is usually a problem when the air bag light try checking that and see if it helps

The air bag code 44 indicates that the air bag computer is not receiving a signal from the right front air bag sensor. This could be caused from defective wiring (loose wire or grounded through chafing) or the sensor being defective.

I was unable to locate code 31 in my book here is a copy of the codes. looks like you just need a fuse for #51. this may fix 31 as well.

Diagnostic Trouble Code Table 1994

AIR BAG DIAGNOSTIC MONITOR DIAGNOSTIC TROUBLE CODE PRIORITY TABLE
Priority Code Component/Fault Description
Highest - No Air Bag Indicator - Inoperative Lamp Circuit or No Ignition
Voltage to Air Bag Diagnostic Monitor

Continuous Air Bag Indicator - Air Bag Diagnostic Monitor
Disconnected or Inoperative
12 Low Battery Voltage
13 Air Bag Circuit Shorted to Ground
14 Primary Crash Sensor Circuit Shorted to Ground
21 Safing Sensor Not Mounted to Vehicle Properly
22 Safing Sensor Output Shorted to Battery Voltage
23 Safing Sensor Circuit Input Feed/Return Circuit Open
24 Safing Sensor Output Feed/Return Circuit Open
32 Driver Side Air Bag Module High Resistance or Open
33 Passenger Side Air Bag Module High Resistance or Open
34 Driver Side Air Bag Module Circuit Low Resistance or Shorted
35 Passenger Side Air Bag Module Low Resistance or Shorted
42 Center Radiator Primary Crash Sensor Feed/Return Open
44 Center Cowl Primary Crash Sensor Not Mounted to Vehicle Properly
45 Center Radiator Primary Crash Sensor Not Mounted to Vehicle Properly
51 Diagnostic Monitor Internal Thermal Fuse - Fuse Blown Due to
Intermittent Short to Ground
52 Backup Power Supply - Voltage Boost Fault
53 Primary Crash Sensor Circuits - Resistance to Ground or Air Bag
Diagnostic Monitor Failure

Lowest - Rapid Continuous Flashing of Air Bag Indicator (No DTC) All Primary

Seems to be a very common problem with Ford. The wiring harness beneath the drivers seat contains the sensors for the airbag system. Go under the drivers seat and secure all the wires and clips. This makes most error lights for the airbags go away. Hope this helps and good luck!

If a concern is detected, the air bag control module will communicate by flashing the warning indicator. A diagnostic trouble code (DTC) is logged by the air bag control module in a nonvolatile memory. For additional information, refer to Diagnosis and Testing in this section.
Lamp Fault Codes (LFC)
Item Part Number Description 1 One flash cycle: Driver air bag trouble code 2 Two flash cycle: Passenger air bag trouble code 3 Three flash cycle: Trouble code common to both driver and passenger air bag circuit 4 Four flash cycle: Safety belt pretensioner trouble code common to both driver and passenger pretensioner circuits 5 Five flash cycle: Driver side air bag trouble code 6 Six flash cycle: Passenger side air bag trouble code 7 Not used 8 Not used

You can't reset it. It's flashing a code. If you tell me the code, I can tell you the proceedure to isolate the fault.

when you start up, there is an 8 second system test and the light is on during this period. Then it flashes out a 2-digit code. The first group of flashes is the first digit and then there is a pause before the second group of flashes which represent the second digit.

flash-flash-flash-pause-flash-flash-flash-flash-flash-flash = code 36

What code is your system flashing?

it is flashing a Lamp Fault Code to tell you what part of your air bag system is faulty. read the number of flashes - pause - number of flashes. Could be 1 digit code or 2 digit code.

What code is it?