P2135 Code on a GMC: Throttle Position Sensor 1-2 Correlation (GMC Guide)

P2135 on a GMC is GM's "Throttle Position (TP) Sensor 1-2 Correlation." The two position sensors inside the electronic throttle body disagree, so the engine computer limits the throttle and shows "Reduced Engine Power." It matters on a GMC because GM put real money behind this code: one special coverage for the V8 Sierra, Yukon, Yukon XL, Savana, Envoy and Canyon, and another for the Canyon and Acadia. And the surprise is in GM's own V8 truck bulletin, which opens with an instruction most shops ignore — "DO NOT replace the throttle body" — then makes an engine computer reprogram mandatory after the repair.

What Does P2135 Mean on a GMC?

Every GMC gas engine with electronic throttle control has no cable between pedal and throttle. A motor in the throttle body opens the throttle plate, and the engine control module (ECM) decides how far. To know exactly where that plate is, the throttle body carries two throttle position sensors reading the same shaft. Their signals move in a fixed relationship as the throttle opens; if that relationship breaks, the ECM cannot tell which one to believe.

GM's truck bulletin 11-06-04-007C gives the setting condition: P2135 sets when "the difference between the TP Sensor 1 and TP Sensor 2 exceeding a calibrated value for more than 2 seconds." The ECM's response is reduced engine power and the check engine light.

That is why P2135 is usually an electrical fault, not a mechanical one. The engine is fine; the sensor, the contacts in the throttle body's sensor cover, the connector or the wiring is not. For the general GM picture, see our P2135 GM guide. This page covers the GMC paperwork.

V8 Sierra, Yukon and Savana: The Sensor Cover

GM technical bulletin 11-06-04-007C (November 2012) is the key GMC document. It names the 2008–2011 Canyon, Savana, Sierra, Sierra Denali and Yukon models, the 2008–2009 Envoy, the 2008–2011 Yukon Two-Mode Hybrid and the 2009–2011 Sierra Two-Mode Hybrid, with GM's V8 engines listed by RPO (LFA, LY2, L20, LMG, LC9, LH6, LMF, LH8, LH9, L76, LS2, LY5, LY6, L92, L96, LZ1, L94, L9H) — the 4.8L, 5.3L, 6.0L and 6.2L truck V8s. On the Canyon and Envoy, that means the 5.3L V8 versions, not the four-, five- and six-cylinder engines.

The repair GM describes is not a throttle body:

• Remove and clean the throttle body, then replace the throttle position sensor cover, GM part 19259452.
• Check the scan tool's TP Sensor 1 and 2 Agree/Disagree parameter through slow and rapid pedal sweeps. It should read Agree; if it reads Disagree, replace the throttle body.
• If P1516, P2101 and/or P2176 are set, replace the throttle body.
• Reprogram the ECM with the latest calibration — GM says all 2008–2011 vehicles "MUST" have this done after the cover is installed — then perform the throttle learn reset.

Two details catch people out. First, on 2011 models the new calibration includes GM's enhanced oil life monitor, which allows a maximum of 7,500 miles (12,000 km) between oil changes. If your 2011 Sierra's oil reminder changed after a throttle repair, that is why. Second, GM's handling rules are strict: do not mount the throttle body in a vise, do not immerse it in solvent or use anything containing MEK, and if the throttle body or its intermediate gear is dropped, abort and fit a new throttle body. GM's labor time was 1.3 hours, or 1.7 hours on the Savana and Express vans, including the reprogram and learn.

Special Coverage 11273

GM backed that repair with Special Coverage 11273. We read revision 11273B (December 2013). Its GMC models are the 2008–2009 Envoy, the 2008–2011 Savana, Sierra, Yukon and Yukon XL, and the 2009–2011 Canyon, all equipped with a V8. GM's condition statement: the throttle position sensor "may cause the engine to run rough and cause the malfunction indicator lamp and/or an Engine Reduced Power message to illuminate."

• Entry code: the dealer had to verify P2135 as current or in history. Without it, the coverage did not apply.
• Repair: "replace the throttle position sensor and reprogram the Engine Control Module," using sensor kit 19259452.
• Term: 10 years or 120,000 miles from the original in-service date, whichever came first, regardless of ownership.

The newest GMCs covered are 2011 models, so for practical purposes the term has passed on every truck it named. A dealer VIN check is still free and will show whether the repair was ever done.

Canyon and Acadia: Special Coverage 14582

A separate program, Special Coverage 14582 (September 2015), "Throttle Body – Reduced Power Mode," named the 2008–2012 Canyon and 2009–2012 Acadia among many GM models. A month later GM revised it as 14582A, which states that 2012 Acadias "are not involved and have been removed." The final GMC list is the 2008–2012 Canyon and 2009–2011 Acadia.

• Entry codes: P2135, P0121 or P0221 current or in history.
• Repair depends on the throttle body supplier. Bosch units get a complete throttle body and gasket. Hitachi units get a throttle position sensor kit, and GM says the Hitachi throttle body "only needs to be replaced if the sensor kit does not correct the condition."
• Term: 10 years or 120,000 miles, whichever came first, regardless of ownership.

The bulletin does not say which Canyon or Acadia engine has which supplier's throttle body, so neither do we; GM told dealers to choose parts by VIN, service information and the parts catalog. As with 11273, the newest vehicles are now well past ten years, so the term has passed for practical purposes, but a dealer VIN check costs nothing.

Older GMCs: P2135 With Other Codes

On earlier GMCs, NHTSA's index lists GM documents in which P2135 appears as part of a group. We could read only the summaries, so treat these as corroborated:

• 3089 — 2003–2006 Envoy, Savana, Sierra and Yukon: service engine soon light and reduced power with P1516; P0120, P0220, P1514, P1515, P1518 and P2135 may also be present.
• 03-06-04-062 (November 2003) — revises step 4 of GM's P2135 diagnostic for the 2003 Envoy, Sierra and Yukon.
• 07-06-04-003 (January 2007) — LK5, L52 and LL8 engines (2006 Canyon and Envoy): reduced power with P1516, P2135, P2138.
• 08-06-04-014 (March 2008) — 2004–2007 Canyon with the 2.8L, 2.9L, 3.5L or 3.7L: P060E, P1516, P2135 and/or P2138 with reduced power, and the summary's instruction is to test and charge the battery.

That last one is the GMC-specific lesson: on an early Canyon, low system voltage was GM's documented trigger for throttle and pedal correlation codes together. Check the battery before you buy a throttle body.

P2135 Is the Throttle, Not the Pedal

GM builds the same two-sensor safeguard into the accelerator pedal, and both codes cause the same reduced power message. P2135 means the sensors in the throttle body disagree; P2138 means the sensors in the accelerator pedal disagree. A pedal will not fix P2135. Where they meet is the 5-volt reference: sensors share reference circuits, so GM diagnoses reference codes first — see our P0641/P0651 guide.

Reduced power is the right response when the ECM cannot trust the throttle, but it arrives without warning, and a loaded Sierra or Yukon that will not accelerate while merging or towing is a hazard. A restart may restore power for a while; it is not a repair.

Symptoms of P2135

• "Reduced Engine Power" message and limited acceleration
• Check engine light on
• Rough running or rough idle — both GM coverages mention it
• Hesitation or no response to the pedal
• Normal power after a restart, then the fault returns
• Companion codes: P0121/P0221, P1516, P2101, P2176, or 5-volt reference codes

Causes and How to Confirm Each

How Is P2135 Diagnosed?

1. Read all codes and freeze frame. Note P2135 with any P0121/P0221, P1516, P2101, P2176 or reference codes.
2. Test the battery and charging system — especially on a 2004–2007 Canyon.
3. Diagnose 5-volt reference codes first if present.
4. Watch TP 1 and TP 2 (or the Agree/Disagree parameter) while slowly and quickly sweeping the pedal with the engine off and key on.
5. Inspect and wiggle-test the throttle body connector and harness.
6. Check your VIN for 11-06-04-007C, 11273 or 14582 involvement and whether the work was done before.
7. Repair by GM's order: sensor cover or kit first where GM specifies it, throttle body only when GM's checks call for it.
8. Reprogram and relearn. On 2008–2011 V8 trucks GM requires the ECM update and throttle learn reset after the cover.

Parts and Cost

GM Documents That Name P2135 on a GMC

No GM bulletin we found names P2135 for a Terrain or a newer Acadia, Sierra or Yukon. Have a dealer check your VIN against current bulletins and coverages rather than relying on any article, including this one.

What Other P2135 Pages Get Wrong

• "Replace the throttle body." On 2008–2011 V8 GMCs GM's bulletin says the opposite and replaces the sensor cover.
• Skipping the reprogram. GM makes the ECM update mandatory after the cover on those trucks.
• Replacing the pedal. P2135 is the throttle body's sensors; the pedal is P2138.
• Ignoring the battery. GM's early Canyon bulletin summary says to test and charge it first.
• "Clean it and it's fixed." Cleaning is a step in GM's procedure, not the cure.
• Assuming a coverage is still open. 11273 and 14582 ran 10 years/120,000 miles and have passed for practical purposes on the GMCs they named.

The Escalade shares GM's V8 truck bulletin; our P2135 Cadillac guide covers its own coverage.

Frequently Asked Questions

Is it safe to drive my GMC with P2135?

It will usually drive in reduced power, but you may not get the acceleration you need to merge or climb, particularly when towing. Treat it as a fix-soon fault and avoid situations where you need full power.

Do I need a new throttle body for my 2010 Sierra?

Not necessarily. GM's 11-06-04-007C for 2008–2011 V8 Sierras says not to replace the throttle body when this condition is found, and to replace the TP sensor cover and reprogram the ECM instead. A throttle body is called for only if GM's checks afterward still fail.

Why did my oil life reminder change after a throttle repair?

On 2011 models, the ECM calibration GM installs with the sensor cover includes the enhanced oil life monitor, with a maximum of 7,500 miles between oil changes.

Is Special Coverage 11273 still active on my Yukon?

The term was 10 years or 120,000 miles from the in-service date, and the newest Yukons covered are 2011 models, so it has passed for practical purposes. A dealer can still check your VIN for free.

My 2006 Canyon has P2135 and P2138 together. What first?

Check the battery and charging system. GM's summary for 2004–2007 Canyons with P2135 and/or P2138 and reduced power says to test and charge the battery, and two correlation codes at once often point at voltage or a shared reference.

Does the Acadia's P2135 coverage apply to a 2012?

No. GM revised 14582 to 14582A specifically to remove 2012 Acadias. The GMC models left are 2008–2012 Canyon and 2009–2011 Acadia.