Help!

p420 means that cat is not working as it should, could be a contaminated cat or a very ricjh mixture. Pull the plugs on the the firewall side of the motor sto see if they are carboned up.

Possible causes:

Use of leaded fuel.
Oil contamination.
Cylinder misfiring.
Damaged HO2S.
Damaged ECT sensor.
Downstream HO2S wires improperly connected.
Fuel pressure too high.
Damaged exhaust system pipe.
Damaged exhaust manifold.
Damaged muffler/tailpipe assembly.
Damaged catalytic converter.

Diagnostic Trouble Code (DTC) P0402 indicates that Self-Test has detected EGR flow at idle.


Possible causes:

EGR valve stuck open.
EGR vacuum regulator solenoid vent plugged or iced.
EVR circuit shorted to GND.
EVR circuit shorted to VREF.
Improper vacuum hose connection.
Plugged/pinched EGR Vacuum Regulator Solenoid vacuum hose.
Plugged EGR tube.
Damaged EGR Vacuum Regulator Solenoid solenoid.
Pinched/iced pressure hoses.
Damaged Differential Pressure Feedback EGR (D.P.F. EGR) sensor.
Damaged PCM.



P1744 TCC Excessive slip detected. (California ONLY). Excessive slip detected during full TCC engagement. Torque converter disengaged. EPC pressure at minimum. May activate MIL.

Just had this on my '97. It was a bad TCC solenoid.

You are going to have to determine the cause. In my case the TCC solenoid coil read a very high resistance around 50 ohms. It should be around 20 or less. They had to replace the solenoid. $430.00