The 133 and 153 are O2 Sensor slow response codes. The 420 is a catalyst efficiency code. I'm surprised it set with the 133 and 153 in memory because the 420 is a comparitive code, i.e. it compares values with the front sensors.
I'd make sure the O2 sensors are receiving 12V on the heater circuit with the key on. Sometimes they'll set a slow response when the heater is either bad or not receiving voltage. Then again, you may just have bad O2 sensors. Most likely, but I'd still ck. for voltage.
There's also this TSB which is a possibility;
Article No.
97-15-22
07/21/97
^ MALFUNCTION INDICATOR LAMP (MIL) - MIL LAMP
ILLUMINATED - DIAGNOSTIC TROUBLE CODES
(DTCS) P0133 AND P0153 STORED IN MEMORY -
EXPLORER WITH 4.0L OR 5.0L ENGINE, AND
MOUNTAINEER WITH 5.0L ENGINE
^ LAMP - MALFUNCTION INDICATOR LAMP (MIL)
ILLUMINATED - DIAGNOSTIC TROUBLE CODES
(DTCS) P0133 AND P0153 STORED IN MEMORY -
EXPLORER WITH 4.0L OR 5.0L ENGINE, AND
MOUNTAINEER WITH 5.0L ENGINE
LIGHT TRUCK:
1996-97 EXPLORER
1997 MOUNTAINEER
CALIBRATION:
6-54G-R05, 6-54G-R11, 6-54G-R12, 7-54G-R12, 6-57B-R10, 6-57R-R10, 6-58B-R10, 6-58R-R10
WARNING : THIS MODIFICATION IS AUTHORIZED ONLY FOR THE LISTED ENGINE. PERFORMING THIS MODIFICATION ON OTHER ENGINE CALIBRATIONS IS UNAUTHORIZED AND COULD CREATE LIABILITY UNDER APPLICABLE FEDERAL OR LOCAL LAWS.
ISSUE:
The Malfunction indicator Lamp (MIL) may illuminate with Diagnostic Trouble Codes (DTCs) P0133 and P0153 stored in memory with no driveability concerns present. This may be caused by an interaction with the On-Board Diagnostics (OBD II) Heated Exhaust Gas Oxygen (HEGO) monitor software and the purge vapor management software, and could result in the above listed Powertrain Control Module (PCM) codes.
ACTION:
Reprogram the PCM using the Service Bay Diagnostic System (SBDS) or the New Generation Star (NGS) Tester. The PCM control strategy was revised to prevent a purge "reset" from occurring while running the HEGO monitor. If a reset occurs while running the HEGO test, the strategy now exits the HEGO test. Refer to the following Service Procedure for details.
SERVICE PROCEDURE
1. For all MIL concerns, conduct normal diagnostics and repair as required.
2. Check to verify vehicle does not have the latest calibration. If it does not, reprogram the PCM with the appropriate calibration, referring to the calibration information using the April 1997 or later CD-ROM.
NOTE : FOR VEHICLES WITH CALIBRATION 6-54G-R05, IT IS MANDATORY TO REPLACE THE FUEL TANK PRESSURE TRANSDUCER (F6DZ-9C052-CA) WHEN UPGRADING TO THE 6-54G-R12 CALIBRATION. FAILURE TO DO SO MAY RESULT IN MIL ACTIVATION WITH DTC CODE P0446 STORED IN MEMORY.
Obtain an Authorized Modification Decal (FPS 8262 - obtainable through DOES II, 25/pkg) and list the date, dealer number, and summary of modifications performed. Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal, and cover it with a clear plastic decal shield.
PART NUMBER PART NAME
F6DZ-9CO52-CA Fuel Tank Pressure Transducer
F6PZ-12A650-DTA Powertrain Control Module (PCM)
F77Z-12A650-BLD Powertrain Control Module (PCM)
F6PZ-12A650-KB Powertrain Control Module (PCM)
F6PZ-12A650-LB Powertrain Control Module (PCM)
F6PZ-12A650-MB Powertrain Control Module (PCM)
F6PZ-12A650-NB Powertrain Control Module (PCM)
OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage And Emissions Warranty
OPERATION DESCRIPTION TIME
971522A Reprogram Powertrain 0.2 Hr.
Control Module (PCM)
971522B Replace Powertrain Control 0.3 Hr.
Module (PCM)
971522C Additional Time To 0.2 Hr.
Replace Fuel Tank
Pressure Transducer
any ideas would be appreciated. Thanks
