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

P2135 on a Cadillac is GM's "Throttle Position (TP) Sensor 1-2 Correlation." The two position sensors inside the electronic throttle body disagree, so the engine computer cuts power and shows "Engine Power is Reduced." Cadillac owners have two separate GM programs behind this code: Special Coverage 14582 for the 2008–2011 CTS and SRX, and Special Coverage 11273 for the 2008–2011 Escalade, ESV and EXT. The Escalade's technical bulletin opens with the line most shops ignore — "DO NOT replace the throttle body" — and then requires an engine computer reprogram that also changes the oil life monitor.

What Does P2135 Mean on a Cadillac?

A Cadillac with electronic throttle control has no cable between the pedal and the throttle. A small motor in the throttle body opens the throttle plate, and the engine control module (ECM) decides how far based on the accelerator pedal and everything else it knows.

Because the ECM must know exactly where that plate is, the throttle body carries two throttle position sensors reading the same shaft. They are scaled differently, so their voltages move in a fixed relationship as the throttle opens. If that relationship breaks, the ECM cannot tell which sensor to believe.

GM's Escalade bulletin 11-06-04-007C gives the setting condition: P2135 sets when the difference between TP sensor 1 and TP sensor 2 exceeds a calibrated value for more than 2 seconds. The ECM's answer is reduced engine power — a deliberately limited throttle — and the check engine light.

That is why P2135 is an electrical fault far more often than a mechanical one. The engine is usually healthy. What failed is the sensor, the contacts in the throttle body's sensor cover, the connector, or the wiring back to the ECM. This guide covers the Cadillac-specific paperwork; for the general GM picture see our P2135 GM guide.

CTS and SRX: Special Coverage 14582

GM Special Coverage 14582 (September 2015), "Throttle Body – Reduced Power Mode," was revised a month later as 14582A (October 2015). Both versions name the 2008–2011 Cadillac CTS and SRX, alongside many Buick, Chevrolet, GMC, Pontiac, Saturn and Hummer models. GM's condition statement: the throttle position sensor "may cause the engine to run rough, cause the malfunction-indicator lamp and/or an engine reduced power message to illuminate, and reduce the engine's power."

The rules, verified from the bulletin:

• Entry codes: the dealer had to confirm P2135, P0121 or P0221 set as current or in history. Without one of them, the coverage did not apply.
• Term: 10 years or 120,000 miles from the original in-service date, whichever came first, regardless of ownership.
• Repair by supplier: Bosch throttle bodies get a complete throttle body and gasket. Hitachi throttle bodies 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."
• Parts: GM listed Bosch and Hitachi throttle bodies plus two Hitachi sensor kits, 19259452 and 19300180, and told dealers to choose by VIN, service information and the parts catalog.

The bulletin does not say which CTS or SRX engine carries which supplier's throttle body, so neither do we. The practical takeaway is GM's own order of repair: identify the throttle body, and if it is a Hitachi unit that takes the kit, the kit comes before a complete throttle body.

The newest Cadillacs named are 2011 models, so for practical purposes the 10-year term has passed on every CTS and SRX it covered. A dealer VIN check is still free, and the bulletin included a customer reimbursement section for owners who paid for the covered repair within the term.

Escalade: Sensor Cover, Not Throttle Body

The Escalade has its own P2135 story, and it is more specific than the CTS and SRX one.

Technical bulletin 11-06-04-007C (November 2012) covers the 2008–2011 Escalade models and the 2009–2011 Escalade Two-Mode Hybrid, with GM's V8 engines listed by RPO (including the 6.2L L92 and L94 used in the Escalade). Its attention line is blunt: "If a vehicle is encountered with this condition, DO NOT replace the throttle body." The repair is to remove the throttle body, clean it, and replace the throttle position sensor cover with GM part 19259452.

Then comes the step that surprises people. GM states that all 2008–2011 vehicles must have the ECM reprogrammed with the latest calibration after the new sensor cover goes on, followed by the throttle learn reset. And on 2011 models, that 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 Escalade's oil-change reminders changed after a throttle repair, this is why.

GM's handling instructions are unusually strict, and they explain why a careless repair fails:

• Do not mount the throttle body in a vise.
• Do not drop or roughly handle electronic throttle parts, and do not immerse them in solvent. Avoid any cleaner containing MEK.
• If the throttle body is dropped at any point, abort and install a new throttle body assembly.

The bulletin also allows a throttle body assembly if the dealer cannot get the sensor kit — a parts-supply fallback, not the preferred fix.

Special Coverage 11273 (11273A, then 11273B in December 2013) put money behind it: 2008–2011 Escalade, Escalade ESV and Escalade EXT with a V8, the same 19259452 sensor kit, and the instruction to "replace the throttle position sensor and reprogram the Engine Control Module." Entry required P2135 current or in history. The term was 10 years or 120,000 miles, so on these model years it has passed for practical purposes. A dealer VIN check is free.

Older Escalades and P2135 with P1516

For the 2003–2006 Escalade, Escalade ESV and EXT, the NHTSA index lists a GM document (3089) for a service engine soon light and reduced power with P1516, noting that P0120, P0220, P1514, P1515, P1518 and P2135 may also be present. A second 2003 Escalade bulletin (03-06-04-062, November 2003) revised a step of GM's P2135 diagnostic. We could read only the index summaries for both, so treat them as corroborated.

The lesson still holds: on an early Escalade, P2135 can arrive alongside throttle actuator codes. Diagnose the whole set, not the one code you recognise.

P2135 Is the Throttle, Not the Pedal

GM builds the same two-sensor safeguard into the accelerator pedal, and the two codes cause the same reduced power message:

• P2135 — the two sensors in the throttle body disagree.
• P2138 — the two sensors in the accelerator pedal disagree. See our P2138 Cadillac guide.

A pedal will not fix P2135, and a throttle body will not fix P2138. Where they meet is the 5-volt reference: sensors share reference circuits, and a short in one can upset others. GM diagnoses reference codes first; our P0641/P0651 guide covers them.

Reduced power is the correct response when the ECM cannot trust the throttle, because a wrong reading could mean unwanted acceleration. But it arrives without warning, and a Cadillac that will not accelerate in a merge is a hazard. Restarting can restore power for a while; it is not a repair.

Symptoms of P2135

• "Engine Power is Reduced" message and limited acceleration
• Check engine light on
• Rough running or rough idle, which both GM coverages list
• Hesitation or no response to the pedal
• Normal power after a restart, then the fault returning
• Companion codes P0121 or P0221 (individual TP sensor performance), or 5-volt reference codes

Causes and How to Confirm Each

How Is P2135 Diagnosed?

1. Confirm it is P2135, not P2138. Throttle versus pedal decides the part.
2. Record every code and diagnose any 5-volt reference or throttle actuator codes first.
3. Check the VIN for 14582A (2008–2011 CTS/SRX) or 11273B (2008–2011 Escalade) — mostly for the repair instructions now, since the terms have passed.
4. Identify the throttle body — supplier and part number — before ordering anything.
5. Inspect the connector and harness at the throttle body for corrosion, damage or a loose fit.
6. Watch TP sensor 1 and 2 on a scan tool through the throttle range while wiggling the harness.
7. Test the reference, low reference and signal circuits per the wiring diagram.
8. Repair as GM directs — sensor cover or kit where it applies, throttle body where it does not.
9. Reprogram and relearn. On a 2008–2011 Escalade, reprogram the ECM; on any Cadillac, perform the throttle learn GM’s procedure calls for, then clear codes and road test.

Parts and Cost

GM Documents That Name P2135 on a Cadillac

Have a dealer check your VIN against current coverages rather than relying on any article, including this one.

What Other P2135 Pages Get Wrong

• "Replace the throttle body." On the 2008–2011 Escalade, GM's bulletin says not to; on Hitachi-equipped CTS and SRX, GM's coverage puts the sensor kit first.
• Forgetting the Escalade reprogram. GM makes the ECM calibration update mandatory after the sensor cover on 2008–2011 models.
• Replacing the pedal. P2135 is the throttle body. The pedal code is P2138.
• "Your Cadillac is still covered." Both 14582A and 11273B ran 10 years or 120,000 miles; for practical purposes they have expired on every Cadillac named.
• Cleaning as the fix. GM's procedure cleans the bore while the throttle body is off, but the repair is the sensor cover or kit. See our throttle body cleaning guide for what cleaning does and does not do.
• Rough handling. GM says a dropped throttle body must be replaced. A bench repair done carelessly creates a new fault.

Frequently Asked Questions

Can I drive my Cadillac with P2135?

Only as far as you need to. Reduced power can come on without warning and limit acceleration in traffic. Restarting may bring power back temporarily, but the fault usually returns.

Is my 2008–2011 CTS or SRX still covered by Special Coverage 14582?

The coverage ran 10 years or 120,000 miles from the in-service date. The newest Cadillacs named are 2011 models, so for practical purposes it has passed. A dealer VIN check is free and will confirm it.

Does my Escalade need a new throttle body for P2135?

Not according to GM. Bulletin 11-06-04-007C for 2008–2011 Escalade models says not to replace the throttle body and to replace the throttle position sensor cover (19259452), then reprogram the ECM and perform the throttle learn.

Why did my Escalade's oil life reminders change after a throttle repair?

On 2011 models, GM's required ECM calibration after the sensor cover includes the enhanced oil life monitor, which allows up to 7,500 miles (12,000 km) between oil changes. The monitor's reminders can look different afterwards.

What is the difference between P2135 and P2138?

P2135 means the two sensors in the throttle body disagree. P2138 means the two sensors in the accelerator pedal disagree. Both cause reduced power, but they are different parts.

Which sensor kit does my CTS or SRX need?

GM listed two Hitachi kits, 19259452 and 19300180, and Bosch-equipped vehicles take a complete throttle body instead. GM told dealers to choose by VIN and the parts catalog, so do the same before ordering.