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Forum > Failed Smog Test > Question

1997 Toyota Camry Failed Smog Test 3 Times

My 1997 Toyota Camry (4 cylinder) failed the smog check 3 times.  The catalyst monitor is not complete. I need to know how to make it "Complete". How many drive cycles or miles must I drive? And, do I replace the front or the rear catalytic converter, or the air fuel ratio sensor?

My Camry was tested two times & failed two times at two separate smog stations that were STAR certified. On the 2nd test, the HC meas 178 (15 mph) and 184 (25 mph) . The CO measurement at 2.73 and 2.31 percent. Prior to test I got the oil changed, the tires inflated, I replaced the spark plugs and the air filter, I put in premium gas, and I drove the car 30 min.

I visited a 3rd smog test and repair shop. The mechanic said the “OBD II” scan code showed several smog related codes as INCOMPLETE. (I had accidentally drained the car battery and this is the cause for the car monitoring to reset.) He recommended I drive the Camry for 400 miles and come back to the shop for another OBD II code reading. I drove the Camry for 275 miles in a couple of days, applying the “DRIVE CYCLE” twice (spent 3 hours on the road). While the engine was thoroughly hot, I re-visited  the smog repair station and the OBD II showed ”Catalyst Status” was not complete; heated Catalyst Status – Not Available. The Catalyst Status is still “Not Complete”. Smog technician said it is premature to fix the catalytic converter. I needed to continue driving the Camry some more to see what the problem code is.

Could you advise me? My Toyota Camry has 285,000 miles and I change the oil every 3,500 miles. Prior to going to the smog repair shop, a second mechanic from another company tested my car and said the rear catalytic converter was not registering any temperature change, but the front catalytic converter was responding to temperature changes within specification and therefore, I should replace the REAR cat. The repair technician from the first smog station said if I change the catalytic converter, it should be the FRONT CAT because this is the front line usage direct from the engine combustion. Another auto repair mechanic said to fix the air filter ratio sensor first; try passing the test and then fix the CAT, if necessary. I’m so confused by all the suggestions and could use some advice.


Answer:

We have to agree with the second smog technicians suggestion of replacing the air fuel ratio sensor before the catalytic converter; either front or rear. One recommendation we do have though is to first have your Toyota Camry diagnosed by a smog check repair station to verify the air fuel ratio sensor commonly known as Oxygen Sensor) is defective before spending the money to replace it. We make this recommendation because of the high CO emissions your Toyota Camry produced during the smog test. It appears your Camry is running "rich"; more fuel then necessary is being delivered to the engine combustion chambers. This may very well be due to a defective AF sensor, but it may also be caused by other sensors as well. For that reason we ask that you get a hands-on diagnosis from a smog station; one which you actually pay for, rather than a suggestion from the technician. Another significantly important sensor which is responsible for correct air/fuel ratio is the mass air flow sensor (MAF). This component tells the ECU (engine control unit) how much air is entering the intake manifold. The computer then adjusts fuel delivery to 14.7:1 (air-to-fuel) in order to produce efficient combustion. You can see how a defective or dirty MAF can disrupt air/fuel ration. Running rich (delivering more fuel then necessary) will result in high CO.

Now as for the drive cycle and CAT monitor... unless the emission system is running properly, the CAT monitor will not run. Your Toyota Camry could have a problem not serious enough to turn on or illuminate the check engine light, but serious enough not to let the CAT monitor run.

Your first step here is to get the CO emission to passing levels. Once that has been accomplished, the ECU should be cleared of any codes, and then a drive cycle be performed in order to complete the CAT (along with other monitors) monitor.


posted by SmogTips Support

 

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