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DTC P1148: Closed Loop Control: Procedure

  1. Turn ignition off. Loosen and retighten 2 engine ground bolts located on intake manifold, near fuel injectors. Loosen and retighten front HO2S to 30-37 ft. lbs. (40-50 N.m). Go to next step.
  2. Disconnect front HO2S and ECM harness connectors. See Figure. Check continuity of White wire between front HO2S harness connector and ECM harness connector terminal No. 46. See Figure. Also check circuit for short to ground and short to voltage. Repair as necessary and retest system. If circuit is okay, go to next step.
  3. Measure resistance between HO2S outer terminals. Resistance should be 2.3-4.3 ohms at 77°F (25°C). Check continuity between both outer HO2S terminals and center terminal. Continuity should not exist. If resistance and continuity are as specified, go to next step. If resistance or continuity is not as specified, replace HO2S and retest system.
  4. Reconnect all harness connectors. Start engine and warm to normal operating temperature. Measure voltage between engine ground and ECM terminal No. 46 by backprobing. See Figure. Increase engine speed to 2000 RPM. The following conditions should exist:
    • MIL goes on more than 5 times in 10 seconds when ECM is in Diagnostic Test Mode II.
    • Measured voltage should be more than .6 volt at least once.
    • Measured voltage should be less than .3 volt at least once.
    • Measured voltage should not exceed one volt.

    If operation is as specified, go to next step. If operation is not as specified, replace front HO2S and retest system.

  5. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.
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