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Old 02-15-2008, 09:37 PM
  #4  
shortyems3307
Member
JOURNEYMAN
 
Join Date: Jun 2004
Location: Hamilton, OH 45013
Posts: 32
Default code po128 and po138

po128 - coolant thermostat/ below thermostat regulating temperature. check your coolant level...if thats ok when your engine is cold see if the thrmostat is stuck open..if thats ok you probably have a coolant temp. sensor failure or wire or connector problem. the po138 is your oxygen sensor picking up a rich exhaust. fuel injection has no choke and has to use coolant temp. to control fuel richness on cold starts. if your coolant is not reaching a specific temp in a specific time the engine light will come on. if the coolant temp. problem is fixed the o2 sensor problem will most likely straighten out. the o2 sensor may or may not clean up with the proper air/fuel mix. hope this helps.... matt.
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