Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

Or, hide this message: temporarily or permanently

HF4 - Check For Any Other DTCs

*** THIS ARTICLE REFLECTS CHANGES MADE BY TSB # 9326B7, December 1993

- Were any other DTCs recorded in HF1 (not including the initial 0420 and/or 0430 DTCs)?

YES -- GO to Powertrain Diagnostic Trouble Code (DTC) Charts to address the DTCs. [1][2]Diagnostic Trouble Code (DTC) Charts

NO -- Non-California applications: GO to HF6. HF6 - Check Fuel Pressure

All others: GO to HF5. HF5 - Check Rear HO2S Wiring