SureTrack Real Fix: Lean Times

Real Fixes from Mitchell 1’s SureTrack® expert information resource are documented issues from actual shop repair orders and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is available at no additional cost in our ProDemand product.

There are lots of components that can affect the fuel system and cause it to be too lean. Follow this Real Fix to see how a code P1128 on this Hyundai Accent was diagnosed and repaired.

2000 Hyundai Accent GL 1.5L

P1128, Replaced Evap Purge Solenoid Valve

The customer state the check engine light is on.

Connected a scan tool and found code P1128 – Long Term Fuel Trim Multiplicative Too Lean. Used the scan tool to monitor live data and found oxygen sensor (B1-S1) voltage was below 450 mV, indicating a lean condition. Used the scan tool to monitor oxygen sensor (B1-S1) with the engine at idle, induced propane into the intake manifold and found the oxygen sensor (B1-S1) signal responded to the rich condition. Connected a fuel pressure gauge to the fuel rail, tested fuel pressure with the key on and engine off, and found the measured fuel pressure was within the specified range of approximately 49.8 PSI. Connected a smoke machine to the intake manifold and induced smoke into the air intake system to check for leaks, but found none. Used the scan tool to monitor live data, used a pair of pinch pliers to block the evaporative emission (EVAP) hose between the intake manifold and EVAP purge solenoid valve and observed the short term fuel trim (Bank 1) parameter began to decrease, indicating a leaking EVAP purge solenoid valve. Attached a vacuum pump to the EVAP purge solenoid valve and tested the valve by applying vacuum. The EVAP purge solenoid valve leaked and did not retain the applied vacuum, which verified the valve was defective.

Replaced the EVAP purge solenoid valve, cleared codes, performed a road test and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned.

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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.