What is Caterpillar Fault Code SPN1058?

SPN 1058 indicates a malfunction in the Aftertreatment Diesel Particulate Filter (DPF) Differential Pressure Sensor circuit. This fault code specifically monitors the pressure sensor that measures the difference in exhaust pressure before and after the diesel particulate filter in Caterpillar excavators equipped with emissions control systems.

The differential pressure sensor is critical for the engine's Electronic Control Module (ECM) to determine when the DPF requires regeneration. This sensor continuously monitors back pressure to assess filter loading and trigger cleaning cycles. When SPN1058 is active, the ECM cannot accurately determine DPF condition, potentially leading to incomplete regeneration, excessive filter loading, or unnecessary regen cycles. For used excavators, this fault can significantly impact fuel economy and cause unexpected downtime if not addressed promptly.

Common Symptoms

• Check Engine Light or Malfunction Indicator Lamp (MIL) illuminated on the instrument cluster
• Excessive or insufficient regeneration cycles, leading to reduced fuel efficiency
• Engine derate or power loss in severe cases where the ECM enters a protective mode
• High Exhaust Temperature (HEXT) lamp warning during normal operation
• Difficulty completing automatic or manual DPF regeneration procedures

Potential Causes

The most common technical causes for SPN1058 on used Caterpillar excavators include:

• Damaged or corroded wiring harness at the DPF differential pressure sensor connector, particularly where the harness routes near hot exhaust components
• Failed differential pressure sensor due to carbon buildup, heat exposure, or internal component degradation common in high-hour machines
• Blocked or damaged pressure sensing tubes connecting the sensor to the DPF inlet and outlet
• Loose or corroded electrical connections at the sensor or ECM terminals
• ECM software issues requiring calibration updates (less common but possible in older firmware versions)
• Physical damage to sensor mounting from debris impact or improper service procedures

How to Troubleshoot and Fix Code SPN1058

Step 1: Visual Inspection Begin by inspecting the differential pressure sensor located on or near the DPF assembly. Check for physical damage, carbon accumulation around sensing ports, and verify both pressure tubes are securely connected without cracks or blockages. On used excavators, carefully examine the wiring harness for abrasion, melting, or corrosion—especially where it passes near exhaust components or frame contact points.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure supply voltage at the harness connector (typically 5 volts with key on). Check sensor resistance values according to Caterpillar specifications (consult service manual for exact values). Inspect the signal wire for proper continuity to the ECM and verify ground circuit integrity. Corroded pins in connectors are extremely common on older machines.

Step 3: Pressure Tube Verification Remove both sensing tubes from the sensor and inspect for carbon blockage or physical damage. Blow compressed air through tubes (with DPF disconnected) to verify they're clear. Many technicians overlook this simple check, which can cause false sensor readings.

Step 4: Component Replacement and Verification If electrical values are incorrect or the sensor shows physical damage, replace the differential pressure sensor with a genuine Caterpillar or quality aftermarket part. After replacement, clear codes using Caterpillar Electronic Technician (Cat ET) diagnostic software and perform a stationary regeneration to verify proper operation. Monitor live data to confirm the sensor provides appropriate pressure readings during various engine loads.

Disclaimer: This guide provides general troubleshooting information. Always consult the specific service manual for your Caterpillar excavator model and consider professional diagnostic assistance for complex emissions system issues. Improper repairs may cause additional damage or emissions compliance problems.