Fuel and Emissions Systems
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System Descriptions (cont'dl
Secondary Heated Oxygen Sensor (Secondary HO2S)
The secondary HO2S detects the oxygen content in the
exhaust gas downstream of the three way catalytic
converter (TWC) and sends signals to the ECM which
checks the efficiency of the TWC. To stabilize its output,
the sensor has an internal heater. The secondarv HO2S
is installed in the TWC.
ztRcoNtaELEMENTSENSORTERMINALS
HEATERTERMINALS
Starting Control
When the engine is started, the ECM provides a rich
mixture by increasing injector duration.
Throttle Position ITP) Sensor
The TP sensor is a potentiometer connected to the
throttle valve shaft. As the throttle position changes, the
sensor varies the signal voltage to the ECM. The TP
sensor is not replaceable apart from the throftle body.
ELEMENTBRUSH HOLDER
gRUSH
11-28
Vehicle Speed Sensor (VSS)
The VSS is driven by the differential. lt generates apulsed signal from an input of 5 volts. The number ofpulses per minute increases/decreases with the speed
of the vehicle.
BEARING
Catalytic Converter System
DTC Troubleshooting
DTC P0420: Catalytic System Efficiency
Below Threshold
NOTE: lf some of the DTCS listed below are stored at
the same time as DTC P0420, troubleshoot those DTCS
first, then recheck for DTC P0420.
P0137, P0138: Secondary Heated Oxygen Sensor(secondary HO2S) (Sensor 2)
P0141: Secondary HO2S (Sensor 2) heater
1. Reset the ECM {see page 1'l-4}, then continue to
step 2 through 5 to reset the readiness code.
2. Start the engine. Hold the engine at 3,000 rpm with
no load (in neutral) untilthe radiator fan comes on.
Drive for about l0 minutes without stopping. Your
speeo can vary.
With the transmission in 4th gear, drive at a steady
speed between 50 62 mph (80-'100 km/h) for
30 seconds.
Repeat step 4 three times. Between each repetition,
close the throttle completely for 1 2 seconds. lf
the engine is stopped during this part of the
procedure, repeat steps 3, 4 and 5.
Check for a Temporary DTC with the scan tool.
Does the scan tool indicate Temporaty DTC
P0420?
YES Check the TWC. lf necessary, replace the
TWC.I
NO Check for readiness code completion. lfthe
readiness is complete, it was a interminent failure,
and the system is OK at this time. lf the readiness
code is incomplete, repeat steps 2 through 5.1
4.
11-167
Connectors and Harnesses
Engine Compartment Wire Harness (Left branch)
AirJuel (A,,/F) ratio sensorBrake fluid level switchCondenser fan motorCruise control actuatorELD unitFog light connectorLeft front ABS wheel sensorLeft front airbag sensorLeft front parking lightLeft front side marker lightLeft lrontturn signal lightLeft headlightLeft hornRadiator fan motorRadiator fan switchSecondary heated oxygen (SHO2S)
Test tachometer connectorWindshield wiper motorUnder'hood fuse/relay boxconnector A {see page 22-44)Under-hood f use/relay boxconnector B (see page 22-44)Under hood fuse/relay boxconnector C (see page 22-44)Under hood fuse/relay boxconnector D (see page 22 44)Under-hood fuse/relay box
Front of engine companmentLeft side of engine compartmentLeft side of engine compartmentLeft side o{ engine compartmentFront of engine compartmentUnder right side of cowl coverUnder'hood f use/relay boxLeft side of engine compartmentLeft side of engine companmentBehind left side of front bumperBehind left headlightBehind left side of front bumperEehind left headlightBehind left headlightBehind front bumperLeft side of engine compartmentFront of engine compartmentLeft side of engine compartment
Left side of engine companmentL.Jnder left side of cowl coverL.Jnder hood fuse/relay box
L.Jnder hood fuse/relay box
L.Jnder'hood f use/relay box
underhood fuse/relay box
Under-hood fuse/relay box
24222
2519
12
17
13202123
3
117
I
10
5
6
l2
2243,l
222223l224
252
5
12
Connector to Harness Index (cont'dl
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22-20
