Symptoms:
Hesitation at slow speeds (between 10 and 30 mph). This was the first symptom. From time to time I would experience severe hesitation on hard acceleration from a stop (for example when merging with traffic on the highway). The car would buck and spit and the Trac Control light would light up and go out.
Eventually the CEL and Trac Control light lit at the same time and stayed on.
At all other speeds and conditions the car ran satisfactorily.
Diagnostics:
I bought a code reader and read a DTC of P0402 (Excessive EGR)
Troubleshooting:
I read the FSM on EGR. It pointed to the EGR valve itself, the EGR position sensor, and the VSV as logical first places to start.
I did not believe the EGR was truly allowing excessive flow since the car idled fine. Excessive flow would create a rough idle or inability to hold an idle. The car has 140K miles on it and I figured it couldn’t hurt to pull the EGR to clean it regardless. I checked operation for smoothness and ability of the valve to seat tightly and did not spot any issues. I cleaned it with throttle body cleaner as best I could and reinstalled it.
Next I checked the ERG Position sensor according to the manual. It did not give the correct resistance readings at the sensor. The harness end was within the voltage range.
I did not believe the VSV was faulty since it would contribute to poor idle issue mentioned above if it was passing too much vacuum. If it was passing too little vacuum, I’d get a different code altogether. I followed the troubleshooting steps outlined in the FSM. All voltage, resistance, and vacuum flows were according to the ranges and specifications in the manual.
Fix:
I replaced the EGR Position Sensor and cleared the DTC memory.
Notes:
The car has been driven about 2 weeks and about 600 miles. No CEL light, no Trac Control light, and no hesitation. The code reader I have can monitor codes as they are written to memory even before they trigger the CEL light. This code requires a 2 trip detection to trigger the CEL. So far the memory indicates no trouble codes detected, not even a single detection.
I was unable to find an EGR Position Sensor on line or at any local parts houses. Most would tell me it they didn’t stock it or it was a dealer part. I wound up ordering it from Toyota for $49.00. Prices ranged from $42 to $64. Nobody stocked the part (including Lexus and Toyota). Turnaround was 2 days.
The part number has changed from 89455-33020 to 89455-33010. Don’t be alarmed if it does not look exactly like the original part. The newer one is smaller and has a different profile.
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