This document is a CAT 0091-08 throttle position troubleshooting guide covering diagnostic code 0091-08 (Throttle Position Invalid, SID 32) for Caterpillar 3406E, C-10, and C-12 on-highway truck engines. It defines the conditions that generate the fault code, the Engine Control Module (ECM) system response, and the required test step to resolve the issue. Published by Caterpillar Inc. under media number RENR1328-08, this single-page reference is essential for diagnosing accelerator pedal position sensor circuit faults.
Official CAT 0091-08 throttle position document details
| Brand | Caterpillar (CAT) |
| Model coverage | C-12 Truck Engine 9NS00001-UP; 3406E, C-10, C-12 On-highway Engines (8YS, 9NS, 5DS, 1LW) |
| System / Group | Troubleshooting — DTCs / SMCS 1913-038 |
| Publication no. | RENR1328-08 |
| Year / Revision | Published 01/10/2008, Updated 16/10/2008 |
| Pages | 1 |
| File size | 0.1 MB |
| Format | |
| Language | English |
Document table of contents
- 0091-08 Throttle Position Invalid (32) — Overview
- Conditions Which Generate This Code
- System Response
- Test Step 1: Accelerator Pedal (Throttle) Position Sensor Circuit — Test
Applicable truck models
This troubleshooting procedure applies to Caterpillar truck engines in the 3406E, C-10, and C-12 families, specifically configurations identified by serial prefixes 8YS, 9NS, 5DS, and 1LW. The documented configuration is the C-12 Truck Engine 9NS00001-UP. These engines are used across various Class 8 on-highway trucks. The diagnostic code 0091-08 is triggered when the ECM detects an accelerator pedal position sensor signal frequency below 150 Hz or above 1050 Hz for more than two seconds after at least three seconds of ECM power-up. When active, the ECM forces throttle position to 0% and the engine remains at low idle; Caterpillar Electronic Technician (ET) displays “DIAG” next to the throttle position status. Resolution requires performing the Accelerator Pedal (Throttle) Position Sensor Circuit test procedure. For additional Caterpillar engine service information, visit Caterpillar official support.
Who needs this CAT 0091-08 throttle position manual
Diesel mechanics and workshop owners working on 3406E, C-10, or C-12 powered trucks need this guide when diagnostic code 0091-08 appears on Caterpillar ET or a handheld code reader. It provides the exact fault conditions, expected ECM behavior, and the single prescribed test step, saving diagnostic time on accelerator pedal sensor circuit issues.
The full PDF is available in the DiagTechPro manuals library; a free account is required to download.
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