Emission Control System
Three Way Catalytic Converter {TWCI (cont'd}
1P0420 Thescantool indicates Diagnostic Trouble Code (DTC) P0420: Catalyst system efficiency belowthreshold.
DescriDtion
This system evaluates the catalyst's capacity by means of the HO2S (Primary and Secondary) output during stable driving
conditions. lf deterioration has been detected during three consecutive driving cycles, the MIL comes on and DTC P0420 will
be stored.
NOTE: lf some of the DTCS listed below are stored at the same time as DTC P0420, troubleshoot those DTCS first. then
troubleshoot DTC P0420.
P0137, P0138: Secondary HO2S (Sensor 2)
P0141: Secondary HO2S (Sensor 2) Heater
Possible Cause
. IWC Deterioration
. Exhaust system leakage
Troubleshooting Flowchart
- The MIL has been reDoried on.- DTC P0420 is stored.
Problem verification:1. Do the ECM/PCM Reset Procedure,2. Start the engine. Hold theengine at 3,000 rpm with noload (in Park or neutrali untilthe radiator fan comes on.3. Connect the SCS service connector.4. Test-drive 40 - 55 mph (64 - 88km/h) for approx. lwo minutes.Then decelerate for at least 3seconds with the throftle completely closed. Then reducethe vehicle speed to 35 mph
156 km/h), and try to hold ituntil the readiness code
Intermittent tailure. system is OKat this time.ls DTC P0420 indicated?
Check the TWC (see section 9).lI nocessary, replace the TwC.
11-200
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'97 model:
The scan tool indicates Diagnostic Trouble Code (DTC) P0441: Evaporative Emission (EVAP) control system
insufficient purge flow.
Description
By monitoring the purge line vacuum with the MAP sensor, the PCM can detect insufficient EVAP control system purge
flow.
Possiblo Cause
. EVAP Purge Control Solenoid Valve
. EVAP Purge Control Solenoid Valve Circuit
. EVAP Control Canister
. Vacuum Lines
. PCM
Troubleshooting Flowchart
EVAP PURGE CONTROL
SO1TNOID VALVE 2P
CoNNECTOR (C108)
(v)
YL
Wire side of female
termrnals
(cont'd)
11-205
Th€ MIL has b€en reooited on.DTC P0441 is .tored.
Problem verificationl1. Start the engine. Hold theengine at 3,000 rpm with noload (in Park or neut.al) untilthe radiator fan comes on.2. Do the PCM Reset Procedure.3. Connect the SCS service con-nector,4. Test drive under following con'ditions on the road.- without any electrical load- Transmission in @ or @position- Engine speed between1 ,2OO - 2,4OO rpfi.- Decelerate from 50 mph (80
km/h)to 15 mph (24 km/h)Intermittent trilure, sydern is OKat this time. Check for Door con-nections or loose wir€3 at C108
IEVAP purge control solonoidvalvol .nd at the PCM.
ls DTC P0441 indicated?
Check tor an open in the wire (lcl
linel:1. Turn the ignition switch OFF.2. Disconnect the EVAP purge
control solenoid valve 2P con-nector.3. Turn the ignition switch ON (ll).
4. Measure voltage between bodyground and the EVAP purge
control solenoid valve 2P con-nector terminal No. '1,
R€pafu open in thc wir6 b€tw€enthG EVAP purge control solenoidvalve and the No. 15 ALTEBNA-TOR SP SENSOR (7.5 A)fuse.
ls there batlery voltage?
(To page 11'206)
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