Diagnostic Aids

Using the "Scan" tester, observe the block learn values under different RPM and airflow conditions. If the conditions for Code 44 exists, the block learn values will be around 150.

• Oxygen sensor pigtail may be mispositioned and contacting the exhaust manifold.
• Check for intermittent ground in wire between connector and sensor.
• A MAF sensor output that causes the ECM to sense a less than normal airflow will cause the system to go lean. If this occurs, disconnect the MAF sensor. If the lean condition is gone, replace the MAF sensor. MAF Tester (J 36101) may be used to test for an out-of-calibration sensor.
• Water, even in small amounts, near the in-tank fuel pump inlet can be delivered to the injectors. The water causes a false lean exhaust condition and can set a Code 44.
• System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving the vehicle at various speeds. Check fuel volume from pump (one pint in 30 seconds) as well as pressure. Also check rubber fuel lines for internal collapse.
• If there is an exhaust leak, outside air may be pulled into the exhaust and past the sensor. Vacuum or crankcase leaks can cause A lean condition.
• If the above tests are okay, replace oxygen sensor.