P1129 on 1996-1999 Honda Civic — Closed Loop Fueling Not Achieved - Bank 2
1 vehicles · 1 makes · $40-$180 repair
How to diagnose and fix P1129: most-reported vehicles
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Honda Civic · 1996–1999
The manifold absolute pressure (MAP) sensor mounted on the throttle body of 1.6L D16 Civics commonly fails as it ages, losing the ability to hold vacuum or drifting out of its 0.5-4.5V calibration range. Because the PCM uses MAP voltage as the primary load input on these speed-density systems, a failing sensor causes the ECU to mis-fuel and mis-time the engine. Failures often set P0107 / P0108 / P1128 / P1129 codes and frequently coincide with cracked vacuum hoses on the upper intake.
Common Symptoms
- Check engine light with P0107, P0108, P1128 or P1129
- Rough idle and stumbling
- Hesitation and loss of power under load
- Rich-running condition and rotten-egg smell from catalyst
- Hard cold starts and emissions test failure
How to Fix
Verify the vacuum supply hose at the throttle body is not cracked or off, then back-probe the MAP sensor signal wire: at key-on engine-off it should read ~2.8-3.0V (atmospheric), dropping to ~1.0-1.5V at idle. If voltage is stuck high, stuck low, or doesn't track manifold vacuum, replace the MAP sensor (Honda P/N 37830-P05-A01 or equivalent). Clear codes and re-test; persistent codes after replacement usually indicate a vacuum leak.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Honda 37830-PAA-S00 MAP sensor setOEMHonda 37830-PAA-S00 (replaces 37830-P0G-S00)
MAP sensor replacement after reference, ground, vacuum passage and signal-response tests prove sensor failure Fitment/availability: Honda catalog fitment covers 1996-2000 Civic DX/EX/HX/Si/CX/GX/LX branches and supersedes 37830-P0G-S00. …
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Sources for this issue (3)
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P1129 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P1129 mean?
P1129 stands for "Closed Loop Fueling Not Achieved - Bank 2." Bank 2 version of P1128: the PCM was unable to establish closed-loop fuel control on the second bank within the expected time, leaving fueling on the open-loop table with degraded economy and emissions.
What are the most common causes of P1129?
The most common causes of P1129 are: Stuck-open thermostat / engine never reaching operating temperature, Bank 2 upstream oxygen sensor or its heater circuit failed, Exhaust leak ahead of the bank 2 sensor, Failed engine coolant temperature sensor, Wiring or connector corrosion at the bank 2 sensor. The specific cause varies by vehicle.
How much does it cost to fix P1129?
Repair costs for P1129 range from $40 to $180, depending on the vehicle and root cause.
Which vehicles are affected by P1129?
Au7o has documented P1129 across 1 vehicle models from 1 manufacturers: Honda.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.