Found this for your fuel code and o2 sensor codes
Diagnostic Trouble Code (DTC) 543/524 indicates a fuel pump secondary circuit failure between the B(+) supply and the FPM connection to the power-to-pump circuit.
Possible causes:
No Starts:
-- Open circuit between the B(+) supply and the FPM connection to the power-to-pump circuit.
-- Fuel pump relay contacts always open.
Engine Starts:
-- Left/Front HO2S short to power
-- Damaged Powertrain Control Module (PCM).
** Does engine start?
NO = fix open in circuit or replace CCRM. RERUN test.
YES = continue
CHECK FRONT/LEFT HO2S FOR SHORT TO POWER
NOTE:
Due to the internal circuitry of the PCM, a Left/Front HO2S signal short to power could produce a DTC 542/543.
* Key off.
* Disconnect left or front HO2S.
* Measure resistance between HO2S signal pin and KEY POWER pin at the HO2S connector.
** Is resistance greater than 10,000 ohms?
NO = replace the O2 sensor. RERUN test.
YES = continue
CHECK HO2S CIRCUIT FOR SHORT TO POWER
* Key off.
* Left or Front HO2S disconnected.
* Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary. Leave PCM disconnected.
* Key on.
* Measure voltage between the HO2S signal at the HO2S vehicle harness connector and chassis ground.
** Is voltage less than 1.0 volt?
YES = replace ECM, reconnect the O2. RERUN test.
NO = fix short circuit, reconnect the ECM and O2. RERUN test.
END
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Continous memory 543
** Also a continous memory code 556/557?
YES = skip ahead to section after next YES/NO quesions
NO = continue
A Continuous Memory DTC 524/543, without the presence of a Continuous Memory DTC 556/557, indicates that during vehicle operation, one of the following has occurred :
-- Open in the B(+) circuit between B(+) and the fuel pump relay.
-- Fuel pump relay contacts opened.
-- Open in the power-to-pump circuit from the CCRM/LFP relay to the FPM splice.
-- Left/Front HO2S circuit short to power.
* Start engine.
* Check for engine stall/stumble while performing the following (also, if possible, listen for fuel pump turning off):
-- Shake, wiggle, bend the fuel pump relay B(+) circuit to the CCRM/LFP relay.
-- Lightly tap the CCRM/LFP relay (to simulate road shock).
-- Shake, wiggle, bend the power-to-pump circuit from the CCRM/LFP relay to the FPM splice.
* Key off.
* Inspect the CCRM/LFP relay connector and B(+) connector terminal for corrosion, damaged pins, etc.
** Is fault indicated/found?
YES = ISOLATE fault and SERVICE as necessary. CLEAR Continuous Memory DTC. RERUN test.
NO = Under certain conditions, a Continuous Memory DTC 524/543 may have been set without a Continuous Memory DTC 556/557, even though a fault has occurred in the fuel pump primary circuit. continue
A Continuous Memory DTC 556/557 indicates a fuel pump primary circuit failure has occurred during vehicle operation. Possible causes are:
-- Open VPWR in the CCRM.
-- Open coil in fuel pump relay.
-- Open in fuel pump circuit (PCM Pin 22).
* Start engine.
* Check for engine stall/stumble while performing the following (also, if possible, listen for fuel pump turning off):
-- Shake, wiggle, bend the EEC-IV vehicle harness fuel pump circuit (Pin 22) between the PCM and the CCRM.
-- Lightly tap the CCRM to simulate road shock.
* Key off.
* Inspect the PCM connector and the fuel pump relay connectors for corrosion, damaged pins, etc.
** Is fault indicated/found?
YES = ISOLATE fault and SERVICE as necessary. CLEAR Continuous Memory DTC. RERUN test.
NO = continue
CHECK LEFT/FRONT HO2S CIRCUIT FOR SHORT TO POWER
NOTE:
Due to the internal circuitry of the PCM, an intermittent left/front HO2S signal short to power could produce a Continuous Memory DTC 542 or 524/543.
* Key off.
* Install breakout box, if applicable.
* Breakout box installed, PCM disconnected.
* Connect a test lamp between the left/front HO2S test (pin 43) and test pin 40 at the breakout box.
* Key on, engine off.
* Observe test lamp for an indication of a fault while performing the following (the light will turn on bright when a fault is detected):
-- Shake, wiggle, bend the left/front HO2S circuit from the HO2S sensor to the PCM.
-- Lightly tap the HO2S sensor (to simulate road shock).
** Is fault indicated?
YES = ISOLATE fault and SERVICE as necessary. CLEAR Continuous Memory DTC. RERUN test.
NO = take to dealer for complicated analysis (sorry)
HOPE THIS HELPS :thumb:
imp2: :thumb:
