OBD-II Diagnostic Trouble Code
P2135 — Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation
P2135 indicates the two throttle position sensor signals, A and B, do not agree with each other within the allowed tolerance. On gas trucks this refers to the two position sensors inside the electronic throttle body; on diesels with an electronic intake throttle valve the meaning can vary by OEM but usually refers to that valve's position sensing.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation
Code
P2135
Category
Powertrain
Subsystem
Throttle
Truck-relevant
Yes
What this means for truckers
P2135 (TPS A/B Voltage Correlation) — primary and secondary pedal sensors disagree. Drive-by-wire safety code — pedal goes to limp mode. Common after a connector issue or one sensor drifts. Replace pedal assembly.
Before you replace parts — try this first
P2135 on the Throttle system is most often failed position sensor in the electronic throttle body (gas) or intake throttle valve (diesel) — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Most vehicles enter a reduced-power or limp mode with a fixed or limited throttle opening, and the check-engine light comes on. Acceleration is weak and gas engines may idle high or stall intermittently.
Common causes
- CommonFailed position sensor in the electronic throttle body (gas) or intake throttle valve (diesel) ($250–$900)
- CommonCorroded or loose connector at the throttle body or intake throttle valve ($80–$300)
- OccasionalWiring fault in one of the two signal circuits or the shared reference or ground ($100–$400)
- RareECM fault or software issue ($300–$2500)
How to fix
Graph both throttle position signals together and compare against the expected relationship
When to use: To confirm which signal is wrong
Inspect and clean the throttle body or intake throttle connector and check terminal tension
When to use: Before replacing parts
Check reference, ground and signal circuits for opens, shorts and voltage drop
When to use: When one signal is consistently offset
Replace the throttle body or intake throttle valve and run the throttle relearn
When to use: When wiring is good and the sensors disagree internally
Affects most
- GMC Sierra 35001 complaint mention this code
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P2100 — Throttle Actuator Control Motor Circuit/Open
- → P2101 — Throttle Actuator Control Motor Circuit Range/Performance
- → P2127 — Throttle/Pedal Position Sensor/Switch E Circuit Low Input
- → P2128 — Throttle/Pedal Position Sensor/Switch E Circuit High Input
- → P2138 — Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation
- → Complaints on GMC Sierra 3500
Frequently Asked Questions
Can I drive with code P2135?
Drive with caution. P2135 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix P2135 on a commercial truck?
Total repair cost ranges $80–$2500 depending on the root cause. The cheapest fix is usually the first one listed below — Failed position sensor in the electronic throttle body (gas) or intake throttle valve (diesel) — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P2135 fail a DOT inspection?
P2135 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P2135 and related codes?
P2135 is closely related to: P2100 (Throttle Actuator Control Motor Circuit/Open), P2101 (Throttle Actuator Control Motor Circuit Range/Performance), P2127 (Throttle/Pedal Position Sensor/Switch E Circuit Low Input), P2128 (Throttle/Pedal Position Sensor/Switch E Circuit High Input). These codes share the same subsystem (throttle) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P2135 is set without the companions, the issue is more isolated.
How do I prevent P2135 from coming back after a repair?
For P2135 (Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation), prevention centers on the throttle system. Clean throttle body at 100K mile intervals. Don't let carbon build up. Avoid extended idle time.