Code
P1525
OLDSMOBILE
P — Powertrain
Throttle Body Service Required
AI status
Completed
Completed
100%
Causes
- Heavy carbon buildup or deposits on the throttle plate and bore
- Faulty or out-of-spec throttle position sensor (TPS)
- Failing throttle actuator/motor or internal throttle body mechanism
- Damaged wiring or poor connectors to throttle body (power, ground, signal)
- Intake vacuum leaks or restricted air passages
- PCM/ECM software or calibration issue requiring relearn or update
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Reduced engine power or limp-home mode engaged
- Poor or unstable idle (high/low/rough idle)
- Delayed or inconsistent throttle response, hesitation
- Stalling at idle or immediately after idle
- Surging or unexpected engine RPM changes
What to check
- Read all stored and pending DTCs and record freeze frame data
- Perform a visual inspection of throttle body, intake tract, and connectors
- Check for vacuum leaks and clogged or restricted intake passages
- Inspect wiring harness and connector pins for corrosion, damage or looseness
- Monitor live data: throttle position (target vs actual), accelerator pedal voltages, MAP/MAF readings
- Command throttle open/closed with a scan tool and observe physical response
Signal parameters
- Throttle position sensor (TPS) voltage: typical 0–5 V range (idle commonly ~0.5–1.0 V; wide open ~4.0–4.5 V) — actual values vary by vehicle
- Accelerator pedal position voltages: dual-sensor correlation should match and be within manufacturer ranges
- Target throttle angle (command) vs actual throttle angle — should follow smoothly when commanded
- Throttle actuator/driver current or duty cycle — may increase when correcting position; abnormal high current indicates binding or motor fault
- MAF/MAP readings and intake air flow should be consistent with commanded throttle opening
Diagnostic algorithm
- Record all current/pending codes and freeze frame; note symptoms and conditions.
- Visually inspect the throttle body, intake passage, PCV and EGR ports for carbon build-up or contamination. Inspect connectors and wiring for damage or corrosion.
- With a scan tool, monitor accelerator pedal sensors, commanded throttle position (target), and actual throttle position. Verify the pedal/TP sensor correlation (no sudden jumps or mismatches).
- Measure supply voltage and ground at the throttle body connector. Verify TPS reference and signal voltages are within expected ranges.
- Command the throttle plate open/closed using a capable scan tool and verify smooth, proportional movement and that actual position follows the target. Listen for unusual noises or binding.
- If throttle sticks or movement is sluggish, remove and clean the throttle body with approved cleaner and inspect for mechanical wear. Recheck operation after cleaning.
- If electrical faults persist, perform resistance/current checks on the actuator motor and TPS per factory procedures. Repair or replace damaged wiring/connectors.
- If components test bad or cleaning does not restore normal function, replace the throttle body assembly and perform recommended relearn/calibration procedures for idle and throttle adaptations.
- Clear codes, perform a drive cycle and verify the fault does not return. If code returns, proceed with component-level replacement or PCM update as guided by factory documentation.
Likely causes
- Carbon and dirt causing throttle plate sticking or slow response
- Degraded TPS signal or sensor drift
- Throttle actuator motor failure or excessive current draw
- Loose/corroded connector or broken wire to throttle assembly
- PCM requesting service because adaptive values out of range
Fault status
Status
Throttle Body Service Required — inspect/clean/test throttle body and related sensors/controls; service recommended.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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