What does P1890 mean on a Chevy?

P1890. Throttle Position Signal Input. Applies to Blazer, S-10, Silverado, Tahoe, Suburban.

What causes P1890 on a Chevy?

Faulty throttle position sensor feeding an invalid signal to the TCM Open or shorted TP signal wire in the transmission control circuit Corroded TP sensor connector skewing the TCM throttle input Misadjusted throttle cable holding TP voltage out of the expected window

How do I fix P1890 on a Chevy?

Read TP voltage sweep on a Tech2 or GDS2 and compare ECM versus TCM readings Test the TP signal circuit end to end for opens and shorts Inspect and adjust throttle cable free play before replacing sensors Verify 5 volt reference and ground at the TP sensor under load Replace the TP sensor only on failed sweep tests, then verify TCM input tracks

Code

P1890

Throttle Position Signal Input

Category: Powertrain - Transmission
Severity: Check Engine Light
Applies to: Blazer, S-10, Silverado, Tahoe, Suburban
Related: No single generic twin. See OBD Codes List

What it means

P1890. Throttle Position Signal Input. This Chevy-enhanced code applies to Blazer, S-10, Silverado, Tahoe, Suburban.

Findings, check these first

Faulty throttle position sensor feeding an invalid signal to the TCM
Open or shorted TP signal wire in the transmission control circuit
Corroded TP sensor connector skewing the TCM throttle input
Misadjusted throttle cable holding TP voltage out of the expected window

Standard procedure

Read TP voltage sweep on a Tech2 or GDS2 and compare ECM versus TCM readings
Test the TP signal circuit end to end for opens and shorts
Inspect and adjust throttle cable free play before replacing sensors
Verify 5 volt reference and ground at the TP sensor under load
Replace the TP sensor only on failed sweep tests, then verify TCM input tracks

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Sources and review

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Last updated 2026-09-19.

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