Solution to New Codes

[Mikz86TA]

2003 4.3 has come up a couple intermittent codes the past week. 1st is P0101 which is MAF/VAF CKT range - performance abd the other has posted 2xs which is P0420. Which is Catalyst Efficiency Below Threshold Bank1. Keep in mind I do have a custom y-pipe and no pre-cat along with a Magnaflow main cat and the rest of the exhaust. It has been months since the pre-cat was removed. If that were the culprit, why does it start to throw it now and not B4? Maybe a bad O2? And if it were from pre-cat removal, is this something a custom-tune could eliviate and ignore? Also I have a Granatelly MAF vehicle and cold-air specific. Its been on since about January or so. I used some MAF specific cleaner from CRC and erased the code, but it re-appreared. Any input? THX, Michel

[viper500hcp]

a custom tune can be used to shut off the post-cat o2 sensor as if it were never there, as far as the MAF code, idk, did you clean all the connections too, or just the sensor wires

[Dogsofjune]

I get P0101 all the time. Usually I either have a leak after the sensor or the maf is a little dirty. I have heard a lot of people complain about how long a Granatelli maf lasts. Not exactly as quality as the stock maf.

I've been runnin' my '03 without a pre-cat for about 5 months now. Never saw that code. Not sure where to lead you with that one.

[Sparky2263]

P0420Notes (javascript:notesWindow('http://alldatapro.com/alldata/PRO~V56741538~C42584~R0~OF34~N/0/89012112/94695002/94695157/119120750/34853741/34857029/34857030/34857663/122915129/125238719/126119967'))CIRCUIT DESCRIPTION
In order to maintain low emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx), the engine controls system uses a 3-way catalytic converter (http://alldatapro.com/alldata/PRO~V56741538~C42584~R0~OD~N/0/89012112/94695002/94695157/119120750/34853741/34857029/34857699/34856671) (TWC). The catalyst within the TWC promotes a chemical reaction, which oxidizes the HC and CO that are present in the exhaust gas. This reaction converts these chemicals into harmless water vapor and carbon dioxide. The catalyst also reduces the NOx which converts into nitrogen. The powertrain control module (PCM) monitors this process using heated oxygen sensor (HO2S) bank 1 sensor 2, which is located in the exhaust stream past the TWC. The HO2S bank 1 sensor 2 produces an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalysts ability to effectively convert the exhaust emissions. If the catalyst is functioning correctly, the bank 1 of the HO2S 2 signal will be far less active than the signal that is produced by bank 1 of the HO2S 1. This indicates that the TWC oxygen storage capacity is below an acceptable threshold.

The PCM performs this diagnostic test at idle. When the conditions for running this DTC are met, the following occurs:


The PCM captures the current rear HO2S rich-to-lean status.
The air-to-fuel ratio transitions from rich to lean or from lean to rich, depending on the captured rear HO2S rich-to-lean status.
The air-to-fuel ratio transitions a second time opposite the first air-to-fuel ratio transition.
The PCM captures the response time of the front and the rear HO2S when the air-to-fuel ratio transitions occur. The HO2S response time goes from less than 300 mV to more than 600 mV , and from more than 600 mV to less than 300 mV.
The PCM measures the time necessary for the rear HO2S voltage to cross a reference rich-to-lean threshold, minus the time necessary for the front HO2S voltage to cross the same rich-to-lean threshold. The difference between the front HO2S time and the rear HO2S time is the oxygen storage capacity of the catalyst. This DTC sets if the time exceeds a predetermined threshold.CONDITIONS FOR RUNNING THE DTC


DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0171, P0172, P0174, P0175, P0200, P0300, P0325, P0327, P0335, P0336, P0341, P0442, P0443, P0446, P0452, P0453, P0455, P0502, P0503, P0506, P0507, P1133, P1134, P1153 are not set.
The intake air temperature (IAT) is between -15°C and +85°C (+5°F and +185°F).
The barometric pressure (BARO) is more than 74 kPa (10.7 psi).
The engine is operating.
The engine coolant temperature (ECT) is more than 70-120°C (158-248°F).
Since the end of the last idle period, the engine speed is more than 900 RPM for the one of the following amounts of time.
40 seconds for manual transmissions
45 seconds for automatic transmissions
The Closed Loop fuel control is enabled.CONDITIONS FOR SETTING THE DTC
The PCM determines that the oxygen storage capability of the TWC has degraded to less than a calibrated threshold.

ACTION TAKEN WHEN THE DTC SETS


The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.CONDITIONS FOR CLEARING THE MIL (http://alldatapro.com/alldata/PRO~V56741538~C42584~R0~OD~N/0/89012112/94695002/94695157/119120750/34853741/34857029/34857030/34857480)/DTC


The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL (http://alldatapro.com/alldata/PRO~V56741538~C42584~R0~OD~N/0/89012112/94695002/94695157/119120750/34853741/34857029/34857030/34857480) and the DTC with a scan tool.