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Home >> Volvo >> 1995 >> 850 GLT, 4D Sedan, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 3 (Engine Controls - Tests W/Codes - Non-Turbo (M/T) - MOTRONIC 4.4) >> Circuit Tests >> DTC 448 - Pulsed Secondary Air Injection System (Pair) Pump Flow Fault >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 1996 Volvo 850. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check status message on scan tool. If status message is PERMANENT FAULT, LEAKAGE, go to next step. If status message is PERMANENT FAULT, FLOW TOO LOW, go step 4). If status message is INTERMITTENT FAULT, LEAKAGE, check exhaust system and PAIR pipe for damage or leakage. Repair as necessary. If status message is INTERMITTENT FAULT, FLOW TOO LOW, go to step 13).
  2. Turn ignition off. Carefully disconnect vacuum hose from solenoid valve. Connect vacuum gauge to solenoid valve. Start and idle engine so it reaches normal operating temperature. Start PAIR pump. If vacuum gauge indicates no vacuum, go to next step. If vacuum gauge indicates vacuum, turn ignition off. Disconnect solenoid valve connector. Connect vacuum gauge to solenoid valve. Start and idle engine so it reaches normal operating temperature. If vacuum gauge indicates no vacuum, check for a short circuit to ground in wiring between solenoid valve terminal No. 2 and ECM connector terminal A37. If vacuum gauge indicates vacuum, replace solenoid valve.
  3. Disconnect PAIR valve from pipe. Leave hoses in place. Turn ignition on. Using scan tool, activate PAIR pump. If no air escapes from PAIR valve outlet, check for air leakage in exhaust system. If air escapes from PAIR valve outlet, replace PAIR valve.
  4. If status message is FLOW TOO LOW, PERMANENT FAULT, turn ignition on. Using scan tool, activate PAIR pump. If a clicking sound is heard from relay and PAIR pump starts, go to step 7). If a clicking sound is not heard from relay and PAIR pump does not start, turn ignition off. Disconnect PAIR pump relay connector "C". Connect voltmeter between PAIR pump relay connector "C" terminal No. 2 and ground. Turn ignition on. Using scan tool, activate PAIR pump. If voltmeter varies between 0-12 volts with a 3-second interval, go to next step. If voltmeter does not vary between 0-12 volts with a 3-second interval, replace PAIR pump relay,
  5. Turn ignition off. Connect ohmmeter between PAIR pump connector "C" terminal No. 2 and ground. If ohmmeter does not read .5-2 ohms, go to next step. If ohmmeter does read .5-2 ohms, replace PAIR pump.
  6. Check PAIR pump ground for contact resistance or poor terminal contact. Repair as necessary. Connect ohmmeter between PAIR pump connector terminal No. 2 and ground. If ohmmeter reads .5-2 ohms, DTC was caused by poor contact at PAIR pump ground. If ohmmeter does not read .5-2 ohms, replace PAIR pump.
  7. Turn ignition off. Disconnect PAIR valve from pipe, leaving hoses in place. Carefully disconnect vacuum hose from PAIR valve. Connect vacuum pump to PAIR valve. Turn ignition on. Using scan tool, activate PAIR pump. Using vacuum pump, pump up vacuum. If air does not escape from PAIR valve outlet when pump is operating, go to next step. If air escapes from PAIR valve outlet when pump is operating, go to step 10).
  8. Turn ignition off. Carefully disconnect PAIR hose from PAIR valve. Turn ignition on. Using scan tool, activate PAIR pump. If air does not escape from end of hose when pump is running, go to next step. If air escapes from end of hose when pump is running, replace PAIR valve.
  9. Turn ignition off. Ensure hose between PAIR pump and PAIR valve is not blocked or leaking. Ensure hose to PAIR pump is not blocked. Repair as necessary. If hoses are okay, replace PAIR pump.
  10. Allow vehicle to cool, then remove exhaust tail pipe. Install Conical Connector (999 5546 ) with Pressure Regulator (999 5544 ) to exhaust system. Adjust pressure to about 58 psi. Depending upon condition of exhaust system a lower pressure may be necessary. Activate PAIR pump. If air is escaping from PAIR pipe, go to next step. If air is not escaping from PAIR pipe, clean PAIR pipe and manifold connector.
  11. Turn ignition off. Using new gasket, reinstall PAIR valve. Carefully disconnect White hose from solenoid valve. Start and idle engine. If there is vacuum in hose, go to next step. If there is not vacuum in hose, ensure White hose, check valve, and connector in intake manifold are not blocked. Repair as necessary.
  12. Turn ignition off. Disconnect hose between solenoid valve and PAIR valve. If hose is leaking or blocked, repair as necessary. If hose is not leaking or blocked, replace solenoid valve.
  13. If status message is INTERMITTENT FAULT, FLOW TOO LOW, check hose between PAIR pump and PAIR valve for pinching or damage. Check vacuum hose with check valve between intake manifold and solenoid valve, and hose between solenoid valve and PAIR valve for pinching and damage. Also check PAIR pump ground terminal and PAIR pump relay power supply terminal for an intermittent open circuit. Repair as necessary.
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