Diagnostic Aids

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: Sec. Air System Elect. Ckt. & Wiring Harness Conn. Term. ID (KC1)

1. 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.
   • Secondary air injection valve inoperative.
   • Secondary air injection solenoid defective or blocked.

   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. If faults are detected, repair as necessary and repeat QUICK TEST. If no faults are detected and Code 311 or 314 is present, go to step 4). If Code 313 is present, go to step 3). If Code 312 is present, go to next step.

2. 2) 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 diverter valve and check valve for faults. If Code 312 is not present, go to step 4).
3. 3) Attempt To Eliminate Code 313
   
   Disconnect and plug vacuum hose at by-pass valve. Repeat KOER SELF-TEST. If Code 313 is present, EEC-IV system is okay. Check by-pass valve for problem. If Code 313 is not present, go to next step.
4. 4) OUTPUT STATE CHECK
   
   Use only a VOM or DVOM for this step. DO NOT  use scan tester. Turn ignition off. Disconnect cruise control servo (if equipped). Connect DVOM negative lead to STO terminal at Data Link Connector (DLC). Connect positive lead to positive battery terminal. Using jumper wire, connect STI to SIG RTN at DLC. See Figure . Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than one volt when test is complete. Depress and release throttle. If voltage increases, OUTPUT STATE CHECK has been entered. go to next step. If voltage does not increase, depress throttle to WOT and release. If STO voltage does not increase, go to CIRCUIT TEST QC.
5. 5) Check Solenoid Electrical Operation
   
   Set DVOM on 20-volt scale. Disconnect AIRB/AIRD solenoids. Connect DVOM positive lead to VPWR terminal and negative lead to AIRB terminal at AIRB solenoid wiring harness connector. While observing DVOM, depress and release throttle several times to cycle output on and off. Repeat test for AIRD solenoid. Connect DVOM positive lead to VPWR terminal 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 9). If both solenoids cycle more than 0.5 volt, stay in OUTPUT STATE CHECK. Reconnect solenoids and go to next step.
6. 6) 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, go to next step.
7. 7) Check Solenoids For Internal Vacuum Leaks
   
   Connect a vacuum pump to AIRB solenoid supply port. Connect a vacuum gauge to AIRB solenoid output port. Apply 15 in. Hg at vacuum source. Observe gauge while depressing and releasing throttle to cycle output on and off. Repeat test for AIRD solenoid. If solenoids cycle on and off, fault is in secondary air injection system (belt, pump, valve or reservoir). If solenoids do not cycle on and off, replace solenoid assembly and repeat QUICK TEST.
8. 8) Codes 553 & 552
   
   Codes 553 and 552 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 battery ground for both solenoids. If either voltage 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.

9. 9) 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.
10. 10) Check Circuit Continuity
    
    Leave ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. 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 wiring harness connector. Measure resistance between AIRD test pin at breakout box and AIRD terminal at wiring harness connector. If either 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.
11. 11) 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 at breakout box. 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 and repeat QUICK TEST. If all readings are 10,000 ohms or more, go to step 12).
12. 12) Check For Short To Power Circuit
    
    Turn ignition off. Leave solenoids and PCM disconnected. Measure resistance between AIRB test pin and test pins No. 37 and 57 at breakout box. Measure resistance between AIRD test pin and test pins No. 37 and 57 at breakout box. If any resistance is less than 10,000 ohms, repair short to power and repeat QUICK TEST. If code is repeated, replace PCM. If all resistances are 10,000 ohms or more, replace PCM and repeat QUICK TEST.