I have been struggling fixing my 2006 chevy tahoe 5.3 non flex. 217000miles
Started months ago with misfire on all cylinders. I replaced the spark plugs, wires, coil packs. New fuel pump and fuel line. New Air filter, crank sensor. After all this no improvement. Finally the truck stopped running and then i discovered the catalytic convertor was clogged...
Make things worse this is a California emissions tahoe. So I tried to save some money and I bought a federal cat and installed it with 4 inch 90 degree defoulers for the downstream 02 sensors. After the install, bank 1 sensor 1 threw a code. I replaced it with a denso and seems to be ok. Shortly after that bank 2 sensor 2 has thrown a p0157 and p2a04 code. I replaced that with a new denso sensor and the codes are still present.
What should I do next to resolve my problem?
Is what I did with the federal cat something that should work? I don't want to pay 1k$ for a new convertor. Thats crazy lol.
Please help me i need this truck for work and I've been driving illegal for months. Already been pulled over and I don't think I can push my luck anymore. Need to get inspection! ✌
While my research is not definitive, the only difference I've been able to discern between a California or New york cat and a Federal cat are the numbers stamped on them.
You really need a scan tool and the shop manual, you've already thrown away a ton of money trying to guess your way through this.
From the shop manual (Get yourself a subscription to it at AllDataDIY):
CIRCUIT/SYSTEM DESCRIPTION
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S
compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream.
The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements
inside the HO2S minimize the time required for the sensors to reach operating temperature. The
engine control module (ECM) supplies the HO2S with a reference, or bias, voltage of about 450 mV.
When the engine is first started, the ECM operates in Open Loop, ignoring the HO2S voltage signal.
Once the HO2S reaches operating temperature and Closed Loop is achieved, the HO2S generates a
voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S
voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.
CONDITIONS FOR RUNNING THE DTC
P0157
● DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120,
P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222,
P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not
set.
● The Loop Status parameter is Closed.
● The Ignition 1 Signal parameter is between 10-18 volts.
● The Fuel Level Sensor parameter is more than 10 percent.
● The TP Sensor parameter is between 3-70 percent.
● DTC P0157 runs the lean test continuously when the above conditions are met for 2 seconds.
CONDITIONS FOR SETTING THE DTC
P0157
● The ECM detects that the HO2S 1 voltage parameter is less than 50 mV.
● DTC P0157 sets within 100 seconds during the lean test when the above condition is met.
CIRCUIT/SYSTEM VERIFICATION
1. If any HO2S heater DTCs are set, perform those diagnostics first.
2. Allow the engine to reach operating temperature.
3. Engine running, observe the affected HO2S parameter with a scan tool.
The pre-catalyst oxygen sensors value should vary from below 200 mV to above 800 mV and respond to fueling changes.
The post-catalyst oxygen sensors value should change more than 200 mV when the throttle is quickly
cycled 3 times from closed to wide open and back to closed after running the engine at 1,500 RPM
for 30 seconds.
4. The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect
for the following sources of contamination:
NOTE:
Refer to Silicon Contamination of Heated Oxygen Sensors Notice .
● A silicon contaminated HO2S
● Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool) or
Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) .
● Engine oil consumption-Refer to Oil Consumption Diagnosis .
● Engine coolant consumption-Refer to Loss of Coolant .
5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset.
You operate the vehicle within the conditions that you observed from the Freeze Frame/Failure records data.
CIRCUIT/SYSTEM TESTING
1. Ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered
down.
2. Ignition OFF, disconnect the harness connector at the appropriate HO2S.
3. Ignition OFF, measure for less than 5 ohms between the appropriate HO2S low signal circuit
terminal A and ground.
○ If more than the specified range, test the appropriate HO2S low signal circuit for an open/high
resistance. If the circuit tests normal, replace the ECM.
4. Ignition ON, verify the appropriate scan tool HO2S parameter is approximately 450 mV.
○ If more than the specified value, test the appropriate HO2S high signal circuit for a short to
voltage. If the circuit tests normal, replace the ECM.
○ If less than the specified value, test the appropriate HO2S high signal circuit for a short to
ground. If the circuit tests normal, replace the ECM.
5. Ignition ON, install a 3A fused jumper wire at the HO2S high signal circuit terminal B. Toggle
the jumper wire between the HO2S low signal circuit terminal A and battery voltage. Verify the
appropriate scan tool HO2S parameter toggles between 0 mV and approximately 1,000 mV.
○ If the appropriate scan tool HO2S parameter does not toggle correctly, test the HO2S high signal
circuit for an open/high resistance. If the circuits test normal, replace the ECM.
6. If all circuits test normal, replace the appropriate HO2S.
