P1112 — Dual Alternator Lower Circuit Malfunction/ Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent Low Voltage

What is the most common cause of P1112?

The most common causes are: contaminated or failed MAF/MAP sensor, wiring or connector faults in the throttle circuit, intake air leaks after the MAF sensor.

Is it safe to drive with P1112?

Drive with caution. Many throttle faults put the car into limp mode with limited power — enough to reach a shop, not for highway trips. If the engine stalls or the pedal stops responding, do not drive.

How much does it cost to fix P1112?

Replace the MAF or MAP sensor — $150–$400; Clean the throttle body — $80–$200; Replace the throttle body assembly — $250–$700. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Will P1112 clear itself?

Sometimes P1112 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What does OBD2 code P1112 mean?

Dual Alternator Lower Circuit Malfunction/ Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent Low Voltage (P1112): a powertrain (engine/transmission) fault affecting the throttle and intake air metering. Short, gentle driving to a shop is usually possible. Most often caused by contaminated or failed MAF/MAP sensor, wiring or connector faults in the throttle circuit, intake air leaks after the MAF sensor.

The P1112 trouble code indicates the Engine Control Module has spotted unstable voltage signals from the Manifold Absolute Pressure sensor circuit, or in some applications a fault in the dual alternator lower circuit tied to throttle monitoring. The ECM stores this code only after detecting the abnormal condition multiple times under specific driving scenarios — not from a single random glitch. That threshold behavior means when P1112 appears, the underlying problem is genuine and repeatable.

This code lives in the powertrain family, directly influencing how the engine manages air intake, fuel mixture, and timing. The MAP sensor tells the control module how much vacuum exists inside the intake manifold; that data shapes the engine's load calculation. If the sensor sends intermittently low voltage readings, the ECM cannot accurately meter fuel or time combustion, and it responds by activating the check engine light and often reducing available power. Freeze frame data stored alongside P1112 pinpoints engine RPM, load, temperature, and speed at the exact moment the fault triggered — use that snapshot to replicate the failure condition during testing.

Typical Symptoms of P1112

• Engine stalls when coming to a stop or during deceleration
• Vehicle enters reduced-power limp-home mode
• Idle runs rough, erratically, or higher than normal
• Throttle pedal feels sluggish or unresponsive
• Check Engine Light illuminated on the dashboard

Common Causes

• Wiring or connector damage in the throttle or MAP sensor circuit (frayed insulation, corroded pins, loose plugs)
• Failed or internally shorted MAP/MAF sensor sending incorrect voltage back to the ECM
• Electronic throttle motor malfunction preventing proper plate movement
• Carbon-fouled throttle body with a stuck or binding plate
• Poor ground connection affecting sensor reference voltage

How to Diagnose P1112

1. Connect an OBD2 scanner, record P1112 as stored, and save the freeze frame data — that snapshot tells you engine load, rpm, coolant temperature, and speed when the failure happened.
2. Look for related diagnostic codes. Secondary codes often expose the root component. Also search manufacturer TSBs by your VIN on themaker's website or nhtsa.gov — many P0xxx codes have documented factory fixes or calibration updates.
3. Perform a hands-on inspection of the throttle body wiring harness and MAP sensor connectors. Look for chafed wires, moisture intrusion, bent terminals, or corrosion buildup.
4. Remove the throttle body and check for carbon deposits or杂物 blocking the plate's full range of motion. Clean thoroughly and verify smooth operation.
5. Monitor live data: throttle position sensor and MAP/MAF readings should respond smoothly as you actuate the accelerator. Erratic jumps or flatline values indicate a failing sensor.
6. Clear P1112, complete a drive cycle that reproduces the freeze frame conditions, then re-scan to confirm the code does not return.

Repair Options and Costs

Tackle the cheapest probable causes before committing to component replacement:

• MAF or MAP sensor replacement (parts and labor): $150–$400
• Throttle body cleaning (parts and labor): $80–$200
• Throttle body assembly replacement (parts and labor): $250–$700

The total bill for fixing P1112 typically falls between $80 and $700 depending on which part is at fault. Accurate diagnosis upfront prevents unnecessary spending — the throttle body assembly is the most expensive fix but rarely the first thing to fail.

Can You Drive With P1112?

Drive with caution. P1112 frequently forces the engine into limp-home mode, which caps available horsepower and torque. That reduced output is sufficient to reach a qualified shop but poses a safety risk if you need to merge onto a freeway or accelerate to avoid a hazard. Stop immediately if the engine stalls or the throttle pedal loses all response — do not continue driving under those conditions. Schedule professional diagnosis promptly, since intermittent faults can worsen without warning.