Code
P1282
CADILLAC
P — Powertrain
Accelerator Pedal Position Sensor 2 Circuit Low Voltage
AI status
Completed
Completed
100%
Causes
- Short to ground in APPS2 signal wire
- Open/high resistance in signal, reference, or ground circuit
- Corroded/damaged sensor connector or pins
- Failed accelerator pedal position sensor (sensor #2)
- Poor 5V reference or ground from PCM
- PCM fault (less common)
Symptoms
- Check Engine Light (MIL) illuminated
- Reduced engine power / limp-home mode
- Poor or delayed throttle response
- Possible inability to start in some designs
- Related throttle control warnings on dash
What to check
- Retrieve freeze frame and status bits with a scan tool; note ignition state when fault set.
- Visually inspect pedal assembly, sensor connector, and wiring harness for damage, corrosion, or moisture.
- Check for additional related codes (APPS1, throttle body, CAN/communication faults).
- Backprobe the APPS2 connector with ignition ON (engine OFF) and measure reference, ground, and signal voltages.
- Wiggle test wiring/connector while monitoring signal for intermittent changes.
- Measure continuity and resistance from the APPS2 connector to the PCM connector (check for short to ground or open).
Signal parameters
- PCM 5V reference: typically ~4.75–5.25 V with ignition ON
- Sensor ground: near 0 V (low impedance to chassis ground)
- APPS2 signal expected to vary smoothly with pedal travel (typical 0.5–4.5 V range depending on design)
- Low-voltage fault threshold: signal below ~0.2–0.3 V (may vary by model/PCM)
- No output (near 0 V) at any pedal position indicates open/short or failed sensor
Diagnostic algorithm
- Step 1 — Confirm: Scan for P1282 and any related codes; record freeze-frame data and ignition state.
- Step 2 — Visual inspection: With ignition off, inspect pedal sensor connector, wiring harness for damage, corrosion, pin push-out, or water entry.
- Step 3 — Reference & ground check: Backprobe connector with ignition ON (engine OFF). Verify PCM 5V reference present and sensor ground continuity to chassis/PCM.
- Step 4 — Signal check: While backprobing, slowly operate the pedal and observe APPS2 signal. It should vary smoothly. If signal is near 0 V or does not change, note result.
- Step 5 — Isolate wiring: If reference and ground are good but signal is low, disconnect sensor and measure for short to ground between signal wire and chassis ground. Repair any short/open.
- Step 6 — Component substitution: If wiring checks good, replace the accelerator pedal sensor assembly with a known-good unit and retest.
- Step 7 — PCM check: If new sensor and good wiring still produce low signal, suspect PCM output or internal ground fault. Verify with manufacturer procedures before replacing PCM.
- Step 8 — Confirm repair: Clear codes, cycle ignition, and test drive to ensure code does not return and throttle response is normal.
- Safety note: Follow vehicle-specific service manual procedures. Do not bypass safety or verification steps; if in doubt, consult OEM wiring diagrams and test procedures.
Likely causes
- Damaged wiring between pedal sensor and PCM (chafing, pinched, rodent chew)
- Corroded or loose connector at pedal assembly
- Failed APPS2 internal circuit
- Faulty PCM voltage reference or internal ground driver
- Contamination or moisture in connector causing short/low reading
Fault status
Status
PCM detected Accelerator Pedal Position Sensor 2 circuit voltage below expected threshold. MIL on; vehicle may enter reduced power/limp mode. Check pedal sensor, connector, wiring, and PCM reference/ground.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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