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If da Engine Coolant Temperature Sensor (ECT) is Below 50 degrees F, then TAB is grounded & sends air to atmosphere; If Between 50 and 190 Degrees F, Bypass Valve sends air to Diverter and to Manifold; If Over 190 Degrees F, it is in closed loop & Air goes to Catalytic Converter; Bypass when at idle/Wide Open Throttle (WOT), and with failing Oxygen Sensor. The fastest way to see if vehicle is in open loop is to see where the air is going; to Catalytic Converter, it is in Closed Loop; to Atmosphere or Manifold it is in Closed Loop, provided the thermactor system is working
Overview in a 96 "...The mechanical AIR system uses a belt-driven pump as well as a check valve to deliver air into the exhaust system where required. The belt-driven air pump runs continuously so a bypass valve and/or diverter valve is used to direct airflow to the exhaust manifold (upstream air), the COC catalyst (downstream air), or directly to atmosphere (bypass/dump). The Mechanical AIR pump flow check monitors the HO2S signal at idle to determine if secondary air is being delivered into the exhaust manifold (upstream). The air/fuel ratio is commanded open-loop rich, the AIR bypass/diverter valves are directed upstream, and the time required for the HO2S signal to go lean is monitored. If the HO2S signal does not go lean within the allowable time limit, a low/no flow malfunction is indicated. (P0411). If the vehicle is equipped with a COC catalyst, the downstream air delivery as well. The air/fuel ratio is commanded open-loop rich, the AIR bypass/diverter valves are directed downstream, and the time required for the HO2S signal to go lean is monitored. If the rear HO2S signal does not go lean within the allowable time limit, a low/no flow malfunction is indicated. (P1411). The PCM outputs that control the bypass and diverter valves are checked for circuit continuity (P0413, P0414 Bypass valve), (P0416, P0417 Diverter valve). Currently, the 4.9L E and F-Series, 5.0L E and F-Series, and 7.5L F-Series incomplete vehicles utilize mechanical air system..." READ MORE
Source: by Ford @@@
http://www.motorcraftservice.com/vdirs/diagnostics/pdf/obdsm963.pdf
System Depiction w/Major Parts in a 5.8
Source: by Steve83 (Steve, That dirty old truck) at
http://www.supermotors.net/vehicles/registry/showmedia.php?id=252398
Thermactor Air Bypass Solenoid (TAB, AIRB, AM1); "...is controlled by the EEC-IV computer and provides vacuum to the Air Bypass/Air Control Valve. With vacuum present, air flows through the secondary air injection system. With no vacuum, the air from the air pump is dumped to the atmosphere. Essentially, this turns the secondary air injection system on or off. The secondary air injection system adds air to the catalytic converter to improve the burning of NOx gases. This reduces emissions..."
Source: by Ted F at tedfelix.com
Vacuum Line Acronyms & Color Codes; Red = Main vacuum; Green = EGR function; Orange = Heat control Valve (exhaust & intake) (AKA heat riser but more complex); Yellow = Distributor advance; White = EGR vacuum (source); Black = Mainly used for the Evaporative emissions control Black = Thermactor ACV or Diverter valve Blue = Throttle Kicker control; Pink = Thermactor Air Bypass Valve (TAB or (BPV) /AIR Bypass (AIRB) valve - ACV (Air Control Valve) is the TAD (Thermactor Air Diverter) Valve (AIR Bypass (AIRB) and AIR Diverter (AIRD) valve combinations) MAN VAC is Manifold Vacuum FPR is Fuel Pressure Regulator EGR is Exhaust Gas Re-circulation Valve SOL V: Thermactor Air Diverter (TAD) Solenoid (SOL V) (AIRD) & Thermactor Air Bypass (TAB) Solenoid EVR is EGR Vacuum Regulator VRESER is the Vacuum Reservoir Can (Tank); V REST on later years is Vapor Valve (Roll-Over) V REST on earlier years such as SEABRONC's 83 is a Vacuum Restictor/delay valve, it delays vacuum for a certain amount of time Carbon Can is Carbon Canister (Charcoal Canister, Vapor Canister, Evaporative Emission (EVAP) Canister) MAP is Manifold Absolute Pressure Sensor AIR BPV is the AIR Bypass (AIRB) Valve; also called the TAB (Thermactor Air Bypass) Valve CPRV is Canister Purge Solenoid Valve/ Canister Purge Solenoid (CANP) VCKV is Vacuum Check Valve CAT is catalytic converter ENG is engine PCV is Positive Crankcase Ventilation Valve
Source: by Steve83 (Steve, That dirty old truck), Seabronc (Rosie, Fred W) & miesk5
