Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1995 Ford RV Cutaway, 1995 Ford Pickup, 1995 Ford F-Super Duty, 1995 Ford Econoline, and 1995 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

PCM uses secondary air injection solenoids to control Air Injection By-pass (AIRB) and Air Injection Diverter (AIRD) valves. AIRB and AIRD are used to direct air to either engine or exhaust system.

Perform this test when instructed by QUICK TEST or if directed by other test procedures. This test is only intended to diagnose:

AIRB/AIRD solenoid valve assembly.
Wiring harness circuits (AIRB, AIRD and VPWR).
Vacuum supply.
Powertrain Control Module (PCM).

To prevent replacement of good components, be aware the following non-EEC related areas may be at fault:

Secondary air injection system (belt, pump, valve or reservoir).
Blocked or restricted secondary air passages in engine.

Fig 1: Secondary Air System Electrical Circuits & Wiring Harness Connector Terminal ID (7.5L)

AIRB WIRE COLOR & TEST PIN IDENTIFICATION

Application	Test Pin No.	Wire Color
7.5L	51	White/Orange

AIRD WIRE COLOR & TEST PIN IDENTIFICATION

Application	Test Pin No.	Wire Color
7.5L	11	Brown

VREF WIRE COLOR & TEST PIN IDENTIFICATION

Application	Test Pin No.	Wire Color
All Models	37 & 57	Red

1) Codes 311, 312, 313 & 314

Code 311 or 314 indicates that secondary air injection system is inoperative. Code 312 indicates that secondary air is incorrectly routed. Code 313 indicates that secondary air is not by-passed when directed. Possible causes for these faults are:

Vacuum hoses leaking, blocked or kinked.
AIRB/AIRD valve inoperative.
Defective AIRB/AIRD solenoids.
Defective air pump.

Check for correct vacuum hose routing to AIRB/AIRD solenoids and by-pass diverter valve. See Vehicle Emission Control Information (VECI) label. Check for kinked or blocked vacuum hoses. Check for kinked or blocked air hoses. Check for disconnected vacuum hoses. Also, check for loose or broken air pump belt (if equipped). If faults are detected, repair as necessary and repeat QUICK TEST. If no faults are detected, go to next step.

2) Check Vacuum Hoses

Carefully check the following vacuum hoses:

Hose from AIRB solenoid to AIRB valve.
Hose from AIRD solenoid to AIRD valve.
Hose from manifold vacuum tee to AIRB/AIRD solenoids.

Check for obstructions, cracks, kinks and leaks. Replace vacuum hoses as necessary and repeat QUICK TEST. If vacuum hoses are okay, and Code 311 or 314 is present, go to step 5). If Code 313 is present, go to step 4). If Code 312 is present, go to next step.

3) Attempt To Eliminate Code 312

Disconnect and plug vacuum hose at AIRD valve. Repeat KOER SELF-TEST. If Code 312 is present, EEC-IV system is okay. Inspect AIRD valve and check valve for faults. If Code 312 is not present, go to step 5).

4) Attempt To Eliminate Code 313

Disconnect and plug vacuum hose at AIRB valve. Repeat KOER SELF-TEST. If Code 313 is present, EEC-IV system is okay. Check AIRB valve for problem. If Code 313 is not present, go to next step.

5) Check AIRD & AIRB Solenoids

Enter output state Diagnostic Test Mode (DTM). See OUTPUT STATE DIAGNOSTIC TEST MODE (DTM) under ADDITIONAL SYSTEM FUNCTIONS. After output state DTM has been entered, disconnect AIRB/AIRD solenoids. Set DVOM to 20-volt scale. Connect DVOM positive lead to VPWR terminal (Red wire) and negative lead to AIRB terminal at AIRB solenoid wiring harness connector. While observing DVOM, depress and release throttle several times to cycle voltage output on and off. Repeat test for AIRD solenoid. Connect DVOM positive lead to VPWR terminal (Red wire) and negative test lead to AIRD terminal on AIRD solenoid wiring harness connector. Cycle AIRD solenoid on and off. If either solenoid does not cycle more than 0.5 volt, remove jumper and go to step 10). If both solenoids cycle more than 0.5 volt, stay in output state DTM. Reconnect solenoids and go to next step.

6) Check AIRB & AIRD For Internal Vacuum Leaks

Reconnect AIRB and AIRD connectors. Connect a vacuum pump to AIRB solenoid supply port. Connect a vacuum gauge to solenoid output port. Apply 15 in. Hg and observe vacuum gauge. Repeat procedure for AIRD solenoid. If both solenoids hold vacuum, stay in output state DTM and go to next step. If either solenoid does not hold vacuum, replace solenoid and repeat QUICK TEST.

7) Check Solenoids For Vacuum Cycling

Connect vacuum pump to solenoid vacuum supply port. Connect vacuum gauge to output port. Maintain 15 in. Hg at vacuum source while depressing and releasing throttle to cycle output on and off. Observe vacuum gauge. Repeat for other solenoid. If either output does not cycle on and off, replace solenoid assembly and repeat QUICK TEST. If both outputs cycle on and off, fault is in secondary air injection system (belt, pump, valve or reservoir).

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 7) to step 9). No test procedures have been omitted.

9) Codes 552 & 553

Codes 552 and 553 indicate voltage output for secondary air injection solenoid did not change when activated. Possible causes for this fault are:

AIRB/AIRD circuit(s) shorted or open.
Fault in solenoid or PCM.

Disconnect both solenoid connectors. Turn ignition on. Measure voltage between VPWR terminal of wiring harness connector and negative battery terminal for both solenoids. If any reading is less than 10.5 volts, repair wiring harness open circuit, and repeat QUICK TEST. If both readings are 10.5 volts or more, go to next step.

10) Measure Solenoid Resistance

Turn ignition off. Leave solenoid connectors disconnected. Measure resistance of both solenoids. If either reading is not 50-100 ohms, replace solenoid assembly and repeat QUICK TEST. If both readings are 50-100 ohms, go to next step.

11) Check Circuit Continuity

Leave ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between AIRB test pin at breakout box and AIRB terminal at vehicle wiring harness connector. Also, measure resistance between AIRD test pin at breakout box and AIRD terminal at vehicle wiring harness connector. If any reading is 5 ohms or more, repair open circuit and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.

12) Check For Short To Ground

Leave ignition off and solenoids disconnected. Measure resistance between AIRB test pin at breakout box and test pins No. 40, 46 and 60. Also, measure resistance between AIRD test pin at breakout box and test pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short to ground. Remove breakout box, reconnect all components, and repeat QUICK TEST. If all readings are 10,000 ohms or more, go to next step.

13) Check For Short To Power Circuit

Turn ignition off. Measure resistance between AIRB test pin at breakout box and test pins No. 37 and 57. Also measure resistance between AIRD test pin at breakout box and test pins No. 37 and 57. If any resistance is less than 10,000 ohms, repair short to power. Remove breakout box, reconnect all components, and repeat QUICK TEST. If code is repeated, replace PCM. If each resistance is 10,000 ohms or more, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST.