Chevrolet P1154 Code: HO2S Transition Time Ratio (Bank 2 Sensor 1)
On a Chevy V6/V8, the bank 2 front O2 sensor rises and falls at clearly different speeds.
At a glance
Severity: Low
- Meaning
- HO2S Transition Time Ratio (Bank 2 Sensor 1)
- System
- Fuel & Air Metering · Powertrain
- Safe to drive?
- Yes, short term
- Typical repair cost
- $40–$800
- DIY difficulty
- Moderate
On Chevrolet V6 and V8 engines the PCM checks each upstream oxygen sensor for balanced response: it averages how long the signal takes to fall from rich to lean and to rise from lean to rich, then compares the two. P1154 means the bank 2 sensor, on the passenger side of GM small-block, Vortec and LS engines, has become lopsided while bank 1 has not. Because only one bank is affected, the useful question is what makes the passenger side different: that sensor's own wear, an exhaust leak at that manifold, a problem with one of the bank 2 cylinders, or damage to that sensor's harness. When P1154 appears without any bank 1 code, shared causes such as fuel pressure are low on the list.
Can I keep driving? Normal driving is fine for now, including towing at moderate loads. Don't ignore a flashing check engine light, though; that would mean an active misfire, which can quickly damage the bank 2 converter.
How to read P1154
- P Powertrain
- 1 Manufacturer-specific
- 1 Fuel & air metering
- 54 Specific fault
Symptoms
- Steady check engine light, engine running normally
- Bank 2 upstream trace shows one slow edge while bank 1 looks crisp
- Bank 2 long-term trim several percent away from bank 1
- Exhaust tick on the passenger side at cold start (when a leak is the cause)
- Occasionally a bank 2 misfire or lean code stored with it
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Bank 2 upstream sensor wearing out unevenly
- Passenger-side exhaust manifold leak or broken stud letting air in ahead of the sensor
- Weak ignition or injector on a bank 2 cylinder sending oxygen-rich pulses past the sensor
- Heat-damaged or chafed bank 2 sensor wiring, or corroded connector
- Bank 2 sensor contaminated by oil or coolant from a leaking gasket on that side
- PCM input or software fault
Diagnosis step by step
Compare the two banks' waveforms
Graph both upstream sensors together at a steady 2,000–2,500 rpm. Bank 1 is your reference: if it shows fast, symmetrical edges and bank 2 has one slow edge, the problem is confirmed to be specific to bank 2.
Tools: OBD-II scanner
Check bank 2 cylinders for misfire
Look at the misfire counters for the even-numbered cylinders (2, 4, 6, 8 on a Chevy V8; 2, 4, 6 on a V6). A cylinder that misfires even occasionally dumps unburned oxygen into that bank and distorts the sensor's response.
Tools: OBD-II scanner
Find passenger-side exhaust leaks
With the engine cold, check for broken manifold studs, soot streaks and gasket blow-by, especially at the rear of the manifold, which is hard to see. Briefly blocking the tailpipe with a gloved hand on a cold engine can make a small leak hiss.
Tools: Flashlight, Gloves
Inspect the bank 2 harness
Follow the sensor pigtail along the passenger side to its connector, looking for melted or stiff insulation and green corrosion in the terminals. Wiggle the harness while watching live data; a jumping signal means a wiring fault.
Tools: Flashlight, OBD-II scanner
Check the sensor tip
After removal, look at the sensor tip: white or gray chalky deposits suggest coolant, black oily soot suggests oil burning on that bank. Fix the source first or the new sensor will go the same way.
Tools: O2 sensor socket
Install and verify
Install a direct-fit sensor, clear the codes and drive at steady speed. Afterwards the bank 2 waveform should look like bank 1, with similar fuel trims on both sides.
Tools: O2 sensor socket, OBD-II scanner
Where the parts are
- 1Upstream O2 sensor
- 2Catalytic converter
- 3Downstream O2 sensor
- 4Diesel particulate filter
- 5Turbocharger
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace bank 2 upstream O2 sensor yourself | Yes | $40–$130 |
| Shop replacement of bank 2 upstream sensor | No | $160–$340 |
| Passenger-side manifold stud extraction and gasket | No | $250–$800 |
| Spark plug / coil or injector repair on a bank 2 cylinder | Yes | $80–$400 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Emissions / smog test impact
Will fail
US state emissions stations read the stored code and the lit check engine light, so the vehicle fails until P1154 is repaired and the O2 sensor readiness monitor has run again.
Frequently asked questions
Where is bank 2 sensor 1 on a Chevy truck?
It's the front oxygen sensor on the passenger-side exhaust, located between the manifold and the catalytic converter. Bank 1, with cylinder 1, is the driver side.
P1154 and P1153 together – what does that mean?
The bank 2 sensor both switches too rarely and responds unevenly, which is a very strong sign that the sensor itself is worn out. If only P1154 is present, check that bank's exhaust and cylinders before replacing the sensor.
Could a misfire cause P1154 even without a misfire code?
Yes. A misfire too small to set a code can still send extra oxygen past the sensor and distort its readings. Watch the per-cylinder misfire counters rather than relying on stored codes.
Do I need to replace both front sensors?
Not necessarily. If bank 1 still looks crisp on the graph, replacing only bank 2 is fine. On very high-mileage engines some owners do both to avoid a second visit.
Sources
- Manufacturer public service information (cross-checked)
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