09-08-2011, 11:25 am
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| Corvette Enthusiast Join Date: Sep 2011 Posts: 2
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|  1994 C4 H64 diagnostic code
First time post - long time reader! having long term issue with my 1994 C4 with 53K miles. Cannot resolve 64 diagnostic code - right bank front O2 sensor lean condition. Replaced sensor twice in last 2 years and condition returns. Using Bosch sensor as replacement. No vacuum leaks- 41psi fuel pressure- 12.5 ohm injector coils (multec) - good continuity from sensor connector to connector of ECU and good sensor heater voltage - no exhaust leaks. Service engine soon light illuminates and engine runs poorly once it warms up and enters closed loop control. I would like to verify that the sensor is actually faulty before I replace it but do not know what voltage to expect? Can anyone help?
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09-20-2011, 06:02 am
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| GM World Class Certified Technician  Join Date: Nov 2006 Location: New Haven Ct Posts: 5,141
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Hi there, The voltage will cycle between 100-850 millivolts, depending on the fuel mixture burned. The key is WHY does it do this ??? Is is possible that you have an air injection check valve that may be leaking oxygen INTO your exhaust manifold ???? I would check to make sure thats not the case. Allthebest, c4c5 | ||||||||||||||||||||
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09-29-2011, 02:13 pm
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| Corvette Enthusiast Join Date: Sep 2011 Posts: 2
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thanks c4c5specialist. I eventually replaced the sensor (bosch) with an AC Delco and the issue was resolved. Bench tested both using a propane torch and the responce was the same - 0V initially warm up to .1V increasing to .9v and hold for 5 minutes. Remove and voltage returns to 0 within 1 minute. Anyway the AC delco has worked perfectly since. One other thing: I actually had and old ACdelco on hand that I replaced last year that I bench tested (didnt know how to do it last year). all worked well until I heated it up for 3 minutes - then the voltage dropeed slowly to 0 with the heat applied! It too is in the trash! Thx again 4 ur help. | ||||||||||||||||||||
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10-01-2011, 05:09 pm
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| Corvette Enthusiast Join Date: Jan 2010 Location: Hobart, Indiana Posts: 14
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When there is a fault, that says you have a lean condition, most of the time the culprit is not the O2 sensor. It is something causing the sensor to give an out of spec reading. It could really be something completely nonrelated to the sensor itself. Look for an exhaust gasket sucking air, or possibly even a injector, that is clogged, causing the condition...hope this helps..Mike
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Linear Mode
