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Typical O2 sensor problems.... Did they use factory O2 sensors?
The 436 code is probably the rear O2 sensor....or the Cat Converter itself crapping out, but here's the troubleshooting guide from the shop manual. Sometimes when you get the code for the rear O2 sensor you need to hook the car up to a ScanTech or Modis digital scanner and actually read the signal (voltage) being sent by the sensor to see if it's in fact bad. But if you just had the O2 sensors changed it could be the Cat is going bad.
Code 4-3-6 (Rear HO2S Compensation)
1) Check for other codes. If Code 4-2-5 is stored, perform
testing for that code first. If Code4-2-5 is not stored, go to next
step.
2) Perform a compression check on all cylinders. Repair as
necessary. If compression is okay, go to next step.
3) Check for air leakage in intake system. Repair as
necessary. If there is no air leakage in intake system, check for air
leakage in exhaust system. Repair as necessary. If there is no air
leakage in exhaust system, check fuel and residual pressure. Repair as
necessary. If fuel and residual pressure are okay, go to next step.
4) Turn ignition on. Connect fuel pressure gauge to system.
Squeeze hose between EVAP valve and intake manifold with Hose Pliers
(115 8957). Code for EVAP system can be set. Start engine and run at
idle until rear HO2S starts operating. Rear HO2S starts operating a
short time after rear HO2S preheating starts.
5) Increase fuel pressure by squeezing hose after fuel
pressure regulator with Hose Pliers (115 8957). Voltage across rear
HO2S terminals should increase to about .8 volt. Remove hose pliers.
Remove instrument cluster hose at intake manifold. If voltage across
rear HO2S terminals drops to about zero volts, retest using new front
HO2S. If voltage across rear HO2S terminals does not drop to about
zero volts, retest using new rear HO2S.
For the 445 code..... I don't know what that is. Could it have been a 4-5-4 misfire code? Or a 4-4-3 Cat efficiency code? Reset it and see if it comes back, then read it again.
Mike
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