have a 2007 Toyota RAV4 I bought from a large car dealer. After two
months the "Check engine" light came on. The Toyota dealer
said it was a defective oxygen sensor, which I had replaced. The
next day the same light came on again. What control does a dealer
have over the check-engine light? Can they set the codes to defer
for a period of time? It seems curious that the light came on two
months after driving off the lot.
it have been more "curious" had the check-engine light
come on the day after you purchased the vehicle? Without knowing the
DTC fault code that has triggered the light this second time, there’s
no way to know whether the recurrence is related in any way to the
original oxygen sensor fault.
original DTC pointed to a failed oxygen sensor, the dealer would
have replaced it and cleared the fault code from the computer’s
memory. That means the light coming on a day later was generated by
a completely new fault, or the same fault recurring. It’s
important to remember that there are several fault codes related to
oxygen sensor(s) and their performance that do not indicate sensor
failure. Replacing an O2 sensor when the fault is a
harness/connector/heater or rich/lean air-fuel mixture won’t
prevent the code from recurring.
To put your
suspicions and paranoia to rest, I don’t believe there’s any way
to manipulate an engine management system to "defer" fault
codes in order to conceal a problem. And of course, to do so would
— like odometer rollback — violate federal law.
Q: I drive a
2003 Chevy Impala with 106,000 miles. Several months ago the
"Service traction system" message came on. I took it to
the dealer and their diagnostic check found code C1218 —
"Pump motor circuit open." Their test found that the ABS
pump motor has had an internal failure and needs to be replaced, at
a cost of over $2,000. Would it be helpful to flush the hydraulic
lines to clean out any debris that might have caused this failure?
Would not replacing the pump have any effect on the ABS braking
to my ALLDATA automotive database, the C1218 code indicates a
voltage issue with the pump motor in the BPMV (brake pressure
modulator valve), part of the EBCM (electronic brake control
module). A special test lamp can test the EBCM’s ability to
control the BPMV. If the lamp lights up, the pump motor circuit
within the EBCM is good.
cause for the ABS and TCS warning lights and "Service traction
system" message is identified and corrected, the ABS and TCS
the hydraulic system to remove moisture and debris every two years
or so is routine maintenance in my book.
Q: I have a
2002 Chevy 2500HD Silverado with 156,000 miles. About six weeks ago
the ABS started activating when stopping from a very low speed with
little pressure on the brake pedal. It sounds like the left front
wheel. No dash warning lights are on before, during or after this
happens. It’s like the wheel speed sensor thinks one of the front
wheels is locking.
exactly what’s happening! Because of an increased air gap between
the wheel speed sensor and reluctor ring on the hub due to a buildup
of rust and debris, the sensor can’t accurately read the
rotational speed of the wheel. And since no rotational reading is
interpreted as lockup by the system, the ABS engages to bleed off
hydraulic pressure to that brake in an attempt to restore rotation.