Ford F150 Pickup. Instruction - part 1514

Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used
to diagnose the exhaust system and downstream HO2S.

Internal damage of a catalytic converter is usually caused by abnormal engine operation upstream of catalyst.
Conditions that produce higher than normal temperatures in the catalytic converter, such as cylinder misfire, are
likely suspects.

Testing

1) For Continuous Memory Only DTC P0420 Or P0430: Check For Misfire Detection Monitor
DTCs
If directed to this test for symptoms only, go directly to step 5). DTC P0420 indicates Bank No. 1 catalyst
system efficiency is below acceptable threshold. DTC P0430 indicates Bank No. 2 catalyst system
efficiency is below acceptable threshold. Possible causes are:

Use Of Leaded Fuel

Faulty HO2S

Faulty ECT Sensor

High Fuel Pressure

Damaged Exhaust System Component

Oil Contamination

Cylinder Misfire

Downstream HO2S Sensor Improperly Connected

Retarded Spark Timing

NOTE:

After each service or repair procedure has been completed, reconnect all
components. Clear DTCs and repeat QUICK TEST procedures to ensure all EEC-
V systems are working properly and DTCs are no longer present.

NOTE:

For additional information on Catalyst Efficiency Monitor, see CATALYST
EFFICIENCY MONITOR under DIAGNOSTIC MONITORING TESTS. For additional
information on exhaust systems, see EXHAUST SYSTEM under CATALYST &
EXHAUST SYSTEMS in THEORY & OPERATION - CNG, FLEX-FUEL &
GASOLINE article.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

Ensure vehicle has not been re-fueled with leaded gasoline and that
engine oil consumption has not increased. Engines that consume oil at a
high rate will deposit high levels of phosphorus on catalyst and reduce
catalyst efficiency.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

Retrieve all Continuous Memory DTCs (MIL or non-MIL). Check for misfire detection monitor DTCs
P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0309, P0310, P0315, P0316 &
P1309. If any misfire codes are present, diagnose those codes first. See DIAGNOSTIC TROUBLE
CODE DEFINITIONS. If no misfire codes are present, go to next step.

2) Check For HO2S Monitor DTCs

Incorrect HO2S signal input (such as a rich or a lean input signal when engine is operating under a lean or
a rich condition) can cause an abnormal temperature increase in catalyst. For possible HO2S monitor
DTCs, see HEATED OXYGEN SENSOR MONITOR under DIAGNOSTIC MONITORS. If any of
these DTCs are present, perform appropriate system test. See

DIAGNOSTIC TROUBLE CODE

DEFINITIONS

. If none of these DTCs were present, go to next step.

3) Check For ECT Or CHT Sensor DTCs
If DTC P0117, P0118, P0125, P0128, P1117, P1285, P1288, P1289, P1290 or P1299 was present in step
1) , perform appropriate system test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS. If none
of these DTCs are present in step 1) , go to next step.

4) Check For Any Other DTCs

If any other DTCs are present in step 1) (not including initial DTC P0420 and P0430), perform
appropriate system test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS. If only DTC P0420
and/or P0430 are present in step 1) , go to next step.

5) Check Rear HO2S Wiring & PCM Connections
Turn ignition switch to OFF position. Ensure HO2S wiring harness is correctly routed, wires are not
crossed and connectors are tight. Repair as necessary. Disconnect PCM connector(s). Inspect connector
for loose, damaged or corroded terminals. Repair as necessary. Check PCM terminals. If PCM terminals
are damaged, replace PCM. Perform DRIVE CYCLES. Ensure CATALYST MONITOR PROCEDURE
is performed to verify repair. If wiring harness, connectors and terminals are okay, go to next step.

NOTE:

ECT or CHT sensor DTCs can indicate thermostat is not operating
correctly or engine coolant level is not filled to specification, possibly
causing higher than normal operating temperatures.

NOTE:

If electrical connections of rear HO2S are interchanged or crossed,
Catalyst Efficiency Monitor Test will fail.

WARNING:

Always refer to safety procedures to reduce possibility of injury. See
FUEL SYSTEM SAFETY PRECAUTIONS.

NOTE:

Fuel pressures above specification can produce an abnormally rich
air/fuel mixture, causing higher than normal catalyst operating
temperatures.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

6) Check Fuel Pressure
Turn ignition switch to OFF position. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE
procedure under FUEL SYSTEMS in appropriate REMOVAL & INSTALLATION article. Perform the
following checks for appropriate fuel system:

Returnable Fuel Systems

Inspect vacuum hose going to fuel pressure regulator for proper installation and cracks. Repair as
necessary. Verify vacuum source to fuel pressure regulator is okay.

Mechanical Returnless Fuel Systems (MRFS)

If applicable, inspect vacuum hose going to fuel rail pulse damper for proper installation and
cracks. Repair as necessary.

Connect scan tool to Data Link Connector (DLC). On vehicles with Electronic Returnless Fuel Systems
(ERFS), monitor fuel pressure by selecting FRP PID from PID/DATA MONITOR & RECORD menu.
On all others, install fuel pressure gauge to Schrader valve on fuel rail. On all models, start engine and
allow to idle. Record FRP PID value or fuel pressure gauge reading at idle. Increase engine speed and
hold at 2500 RPM for one minute. Record FRP PID value or fuel pressure gauge reading with engine
speed increased. Compare fuel pressure readings with fuel system pressure specifications. See Fig. 167. If
fuel pressure is within specification, remove fuel pressure gauge (if applicable) and go to next step. If fuel
pressure is not within specification, go to TEST HC, step 4).

7) Check For Obvious Leak Sources In Exhaust System
Inspect complete exhaust system from exhaust manifold to tailpipe for leaks, cracks, loose connections or
punctures. Repair as necessary. Perform DRIVE CYCLES. Ensure CATALYST MONITOR
PROCEDURE is performed to verify repair. If exhaust system is okay, go to next step.

8) Check For Obvious Restrictions In Exhaust System
Inspect complete exhaust system for collapsed areas, dents or excessive bends. Repair or replace as
necessary. Perform DRIVE CYCLES. Ensure CATALYST MONITOR PROCEDURE is performed to
verify repair. If exhaust system is okay, go to next step.

9) Check For Excessive Exhaust Back Pressure
Install an exhaust back pressure tester and follow tool manufacturer's installation and testing instructions

NOTE:

If a catalyst is in series with a leaking exhaust system, it can fail Catalyst
Efficiency Monitor test.

NOTE:

A slight pressure in exhaust system is normal, but excessive exhaust back
pressure seriously affects engine operation. Causes of high exhaust back
pressure are dents or obstructions in exhaust pipe, or a plugged catalytic
converter or muffler.

NOTE:

If an exhaust back pressure tester is not available, go to step 10).

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

(if available). Exhaust back pressure when measured near exhaust manifold and at normal engine
operating temperature should not exceed 3 psi (20.7 kPa) at idle, and 8 psi (55.2 kPa) at wide open
throttle under load. If exhaust back pressure test indicates a restriction, repair restricted component(s) as
necessary. Perform DRIVE CYCLES. Ensure CATALYST MONITOR PROCEDURE is performed to
verify repair. For further diagnosis of LACK OF POWER, LOSS OF POWER, or NO START symptom,
return to SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE
article. If exhaust back pressure test does not indicate a restriction and you were directed here for DTCs
P0420 or P0430, catalytic converter is chemically inactive. Replace catalytic converter. Perform DRIVE
CYCLES. Ensure CATALYST MONITOR PROCEDURE is performed to verify repair. If directed here
for LACK OF POWER, LOSS OF POWER, or NO START symptom, return to SYMPTOMS in
TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article for further testing.

10) Check Manifold Vacuum For Indication Of Excessive Exhaust System Restriction
Install tachometer. Connect vacuum gauge to intake manifold vacuum source. Place transmission in
Neutral. Start engine and gradually raise engine speed to 2000 RPM. Manifold vacuum reading should
increase to more than 16 in. Hg (54 kPa). Allow engine speed to return to idle. Turn ignition switch to
OFF position. If manifold vacuum reading was as specified, go to next step. If manifold vacuum reading
did not reach specified level, go to step 12) to check for excessive exhaust system restriction.

11) Check Manifold Vacuum For Indication Of Moderate Exhaust System Restriction

Leave transmission in Neutral and tachometer and vacuum gauge connected. With engine still idling,
gradually raise engine speed to 2000 RPM. Observe vacuum gauge reading response while maintaining
increased engine RPM. If an exhaust system is free of restrictions, manifold vacuum increases quickly to
16 in. Hg (54 kPa) as increased RPM is maintained. If exhaust system is restricted, manifold vacuum
increases slowly to 16 in. Hg (54 kPa) as increased RPM is maintained. If manifold vacuum is slow to
raise to 16 in. Hg (54 kPa), go to next step to check for a moderate restriction. If manifold vacuum is
okay, no indication of exhaust leak or restriction has been detected. If directed here for DTCs P0420 or
P0430, catalytic converter is chemically inactive. Replace catalytic converter. Perform DRIVE
CYCLES. Ensure CATALYST MONITOR PROCEDURE is performed to verify repair. If directed here
for LACK OF POWER, LOSS OF POWER, or NO START symptom, return to SYMPTOMS in
TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article for further testing.

12) Check Manifold Vacuum With Exhaust System Disconnected From Exhaust Manifold
Leave tachometer and vacuum gauge connected. Disconnect exhaust pipe from exhaust manifold. Start
engine and gradually raise engine speed to 2000 RPM. Observe vacuum gauge reading response while
maintaining increased engine RPM. If manifold vacuum is okay, exhaust restriction is downstream of
exhaust manifold. Reconnect exhaust system to exhaust manifold and go to next step. If manifold vacuum
is low or slow to respond, restriction is present in exhaust manifold. Check exhaust manifold for

NOTE:

Vacuum gauge reading may be normal when engine is first started and
idling. However, excessive restriction in exhaust system will cause intake
manifold vacuum to decrease with engine at a steady or constant idle
speed.

NOTE:

An intake manifold gasket leak can cause vacuum gauge reading to
remain below normal range.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

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