Did more reading of those Instructables comments. Apparently a P0138 or P0139 is an issue that some people have.
P0139 (P0159 for bank 2 which is the bank this issue is in) sets if the engine goes to DFCO and the downstream O2 takes too long to register the rich/lean transition (presumably high to low voltage). And it sets if the transition is longer than 1 second. So that's cheeky. Seems like a way to detect the filter circuit that I'm installing here. The recommended components were 1M ohm and 4.7 uF. That gives a time constant of 4.7s which seems long. So I guess I'll do the 1M ohm and 1 uF for a 1 second time constant.
DTC P0139 or P0159
Circuit Description
The heated oxygen sensor (HO2S) produces a voltage that varies between 100-900 mV under normal operating conditions. The engine control module (ECM) produces a bias voltage on the HO2S signal circuit of 420-480 mV. The reference ground for the sensor is provided through the ECM. The ECM monitors the signal voltage to determine if the exhaust is lean or rich. The oxygen sensor voltage is high when the exhaust is rich, and low when the exhaust is lean. The ECM constantly monitors the HO2S signal during the Closed Loop operation. If the ECM detects that the decel fuel cut-off rich-to-lean transition time is too long, DTC P0139 will set for bank 1 sensor 2, or DTC P0159 will set for bank 2 sensor 2.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0139 HO2S Slow Response Bank 1 Sensor 2
• DTC P0159 HO2S Slow Response Bank 2 Sensor 2
Conditions for Running the DTC
• DTCs P0021, P0024, P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0135, P0137, P0138, P0139, P0140, P0141, P0151, P0152, P0155, P0157, P0158, P0159, P0160, P0161, P0201-P0208, P0221, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0274, P0276, P0277, P0279, P0280, P0282, P0283, P0300, P0301-P0308, P0335, P0336, P0340, P0341, P0345, P0346, P0351-P0358, P0365, P0366, P0390, P0391, P0442, P0443, P0446, P0449, P0453, P0454, P0455, P0458, P0459, and P0496 are not set.
• The ECT Sensor parameter is more than 66°C (151°F).
• The Vehicle Speed Sensor parameter is between 5-180 km/h (3-112 mph).
• The calculated catalytic converter temperature is more than 520°C (968°F).
• DTC P0139 or P0159 runs continuously once the above conditions are met.
Conditions for Setting the DTC
The ECM detects that the decel fuel cut-off and rich-to-lean transition time has exceeded 1 second.
The P0138 (P0158 for bank 2) is basically the opposite. Instead of taking too long to go low, this sets if the voltage stays too high for too long. And the time parameter is more than 2V for 1.6 seconds.
DTC P0138 or P0158
Circuit Description
The heated oxygen sensor (HO2S) produces a voltage that varies between 100-900 mV under normal operating conditions. The engine control module (ECM) produces a bias voltage on the HO2S signal circuit of 420-480 mV. The reference ground for the sensor is provided through the ECM. The ECM monitors the signal voltage to determine if the exhaust is lean or rich. The oxygen sensor voltage is high when the exhaust is rich, and low when the exhaust is lean. The ECM constantly monitors the HO2S signal during the Closed Loop operation. If the ECM detects an HO2S voltage that stays above a specified value, DTC P0138 will set for bank 1 sensor 2, or DTC P0158 will set for bank 2 sensor 2.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0138 HO2S Circuit High Voltage Bank 1 Sensor 2
• DTC P0158 HO2S Circuit High Voltage Bank 2 Sensor 2
Conditions for Running the DTC
• DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0131, P0132, P0133, P0135, P0137, P0139, P0140, P0141, P0151, P0152, P0153, P0155, P0157, P0159, P0160, P0161, P1137, P1138, P1157, P1158 P2231, P2234, P2237, P2240, P2243, P2247, P2251, P2254, P2626, P2629 are not set.
• The engine is running.
• DTC P0138 or P0158 runs continuously once the above conditions are met.
Conditions for Setting the DTC
The ECM detects that the HO2S parameter is more than 2 volts for longer than 1.6 seconds.
So I guess this "informs" me to keep the time constant to 1s? I'm kind of reaching here but it's worth a try for science.
Here is my circuit diagram. I wired the cap on the wrong side of the resistor the first time.
STS B2S2 jumper circuit.png
I did look up the wire positions so I modify the right wires, and I've labeled both ends of my pigtails. The other good news is I am using ceramic caps so they are not polarized for my convenience.
20210418_121852.jpg
Still doesn't work. Getting P1158 and P0161 as pending codes. The FSM says they can not both set at the same time. I don't understand the heater code. The sensor code I get because I can visually tell voltage is not behaving per the criteria for setting the code (voltage doesn't drop to below 30mV during DFCO for 5 seconds). I can plainly see it goes to 0.390V and sits when it should be 0V. So that code checks out. I think that is because I am using a ceramic cap which is non-polarized. I think it's causing the issue so I need to redo with an electrolytic cap. Argh.
I triple and quadruple checked my wiring. I can't find any issues with the actual pinout setup I am using. Best I can figure is the voltage is getting screwed up because of the ceramic cap and SOMEHOW this also triggers the pending heater code (makes no sense at all though).
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