Hello fellow members,
Hopefully someone on this thread could help me out. I've already posted once on the other thread referring to the non-fouler fix. That was about 2 months ago and no one replied. Hope someone here could share some knowledge.
I drive a 2001 Protege ES 2.0L. Have about 97k miles on it now. I know my primary cat is going bad because I'm getting code P0421 on and off for the last few months.
I was planning to put in the non-fouler fix, but just recently started getting a new code P0037. I believe that is my second o2 sensor going bad? Or do you think it's a false reading due to the bad cat?
Will the non-fouler work on a bad cat or only for headers? (I'm planning to leave the stock primary cat in and just do the non-fouler)
Now will a non-fouler trick work if the o2 sensor was defective? Thanks for any input!
DTC P0421 Warm-up catalyst system efficiency below threshold
DETECTION
CONDITION
PCM compares the number of HO2S (front) and HO2S (rear) inversions for a predetermined time. PCM
monitors the number of inversions the rear side performs while the front side inverts for a specified number
of times when the following monitoring conditions are met. PCM detects the inversion ratio. If inversion
ratio is below threshold, PCM determines that catalyst system has deteriorated.
MONITORING CONDITIONS
Engine speed is 1,5003,000 rpm.
Calculated load is 1548%(*1).
Vehicle speed is 28120 km/h {17.374.5 mph}.
*1: Maximum calculated load value varies depending on engine speed.
Diagnostic support note
This is an intermittent monitor. (CATALYST)
MIL illuminates if PCM detects the above malfunction conditions in two consecutive drive cycles.
DIAGNOSTIC MONITORING TEST RESULTS is available.
PENDING CODE is stored if PCM detects the above malfunction condition during first drive cycle.
FREEZE FRAME DATA is available.
DTC is stored in PCM memory.
DTC P0037 HO2S heater (rear) circuit low
DETECTION
CONDITION
PCM monitors HO2S heater (rear) control signal at PCM terminal 93. If PCM turns HO2S heater (rear) off
but voltage at terminal 93 still remains low, PCM determines that HO2S heater (rear) circuit has
malfunction.
Diagnostic support note
This is an intermittent monitor (O2 sensor heater).
MIL illuminates if PCM detects the above malfunction condition in two consecutive drive cycles.
PENDING CODE is available if PCM detects the above malfunction condition during first drive cycle.
FREEZE FRAME DATA is available.
DTC is stored in PCM memory.
POSSIBLE
CAUSE
HO2S (rear) malfunction
Open circuit between ignition switch terminal C and HO2S (rear) terminal C
Open circuit between HO2S (rear) terminal D and PCM terminal 93
Short to ground circuit between HO2S (rear) terminal D and PCM terminal 93
Poor connection at HO2S (rear) or PCM connector
PCM malfunction
the non-fouler trick would work for the P0421 if the O2 sensor isn't that bad, but won't do anything for the heater circuit. since your also getting a P0037 (rear heater circuit) I'd say check your rear O2 wiring for shorts/grounds, if everything looks good i would replace the sensor.
97k miles, if your O2 sensors have never been replaced, good chance your rear is toast. People say the protege O2 sensors don't last too long. and if you can spare the change i would replace the front as well. If your primary (front) O2 sensor is bad your engine won't be getting the corret AFR and you can suffer power loss and bad fuel economy