P1128 TPS Signal Above Expected Range
The P1128 code on Chrysler, Dodge, and Jeep vehicles indicates that the throttle position sensor (TPS) is reporting a voltage higher than expected for the current engine operating conditions. While the TPS signal is within its normal voltage range, the PCM detects a mismatch between the TPS reading and other engine parameters such as MAP sensor pressure, RPM, or MAF airflow. The PCM compares the TPS signal to predefined engine models; when a persistent discrepancy occurs where the TPS indicates a more open throttle than conditions justify, this manufacturer-specific fault code is set.
01. Most Common Causes
- Misadjusted or improperly calibrated TPS sensor mounting
- Internal mechanical wear of the TPS causing erratic high readings
- Abnormal resistance in the TPS signal circuit due to corroded or sulfated connectors
- Excessive resistance in the 5V reference circuit wiring
- Faulty ground return for the TPS sensor
- Carbon buildup or dirt on the throttle plate altering actual vs. indicated position
- Intermittent TPS sensor failure
- Mechanical issue in the throttle mechanism (stuck cable, damaged return spring)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor acceleration or hesitation
- Reduced fuel economy
- Rough idle or stalling
- Transmission shifting issues (if applicable)
03. Step-by-Step Diagnosis
Scan for codes and verify P1128 is present; check for other related codes.
Inspect TPS connector and wiring for corrosion, damage, or loose connections.
Measure TPS signal voltage at idle and wide-open throttle; compare to specifications.
Check throttle plate for carbon buildup; clean if necessary.
Test TPS sensor resistance and continuity in the circuit.
Verify throttle cable operation and return spring tension.
1. Frequently Asked Questions
Is it safe to drive?▼
You can usually drive short distances, but the vehicle may experience reduced performance, poor fuel economy, or stalling. It's best to diagnose and repair promptly to avoid further issues.
How much does it cost to fix?▼
Repair costs typically range from $100 to $400, depending on whether the TPS sensor needs replacement, wiring repairs, or throttle cleaning. Labor and parts vary by vehicle model.