What is Caterpillar Fault Code EID1137?

Fault Code EID1137 indicates an abnormal voltage condition detected in the aftertreatment diesel exhaust fluid (DEF) pump circuit, specifically signaling a high voltage or open circuit failure. This diagnostic trouble code (DTC) is generated when the Electronic Control Module (ECM) detects voltage readings outside the expected operating range for the DEF pump control circuit, typically above 4.5 volts when a lower voltage is expected.

This code is critical for Caterpillar excavators equipped with Selective Catalytic Reduction (SCR) aftertreatment systems. The DEF pump supplies urea solution to the SCR catalyst to reduce nitrogen oxide (NOx) emissions. When EID1137 is active, the emission control system cannot function properly, potentially leading to engine derate and compliance violations. For used excavators, this fault often appears due to aging electrical components or environmental exposure affecting the DEF system wiring.

Common Symptoms

• Amber malfunction indicator lamp (MIL) illuminated on the instrument cluster
• DEF system warning messages displayed on the operator monitor
• Engine power derate after a predetermined time period if fault remains unresolved
• Reduced DEF dosing or complete cessation of urea injection into the exhaust stream
• Increased exhaust emissions and potential failure of emissions testing

Potential Causes

The most common technical causes for EID1137 on used Caterpillar excavators include:

• Open circuit in DEF pump wiring harness caused by connector corrosion, wire breakage, or terminal damage
• Failed DEF pump motor with internal open circuit or damaged windings
• Damaged or corroded electrical connectors at the DEF pump or ECM connection points
• Chafed wiring harness at known rub points near the DEF tank mounting area or along the chassis frame
• ECM internal fault affecting the DEF pump driver circuit (less common)
• Faulty DEF pump relay or blown fuse in the power supply circuit

How to Troubleshoot and Fix Code EID1137

Step 1: Visual Inspection Begin by thoroughly inspecting the DEF pump wiring harness from the pump to the ECM connection. On used excavators, check for visible wire damage, particularly where harnesses route near moving components or sharp edges. Examine all electrical connectors for corrosion, pushed-out pins, or moisture intrusion—common issues on machines with high operating hours.

Step 2: Electrical Testing Using a digital multimeter (DMM), perform voltage and continuity checks. With ignition on and engine off, measure voltage at the DEF pump connector. You should see battery voltage (approximately 12-14V) on the power supply wire. Check for continuity between the pump ground and chassis ground (should read less than 1 ohm). Test the control signal wire from the ECM for proper voltage range during pump operation using Caterpillar Electronic Technician (Cat ET) diagnostic software.

Step 3: Component Testing and Replacement If wiring tests pass, measure the DEF pump resistance according to Caterpillar specifications (typically 3-6 ohms across pump terminals). An open circuit (infinite resistance) confirms pump failure. For used machines, also inspect the DEF pump relay and associated fuses. Before replacing components, clean all connector terminals with electrical contact cleaner and apply dielectric grease to prevent future corrosion.

Step 4: System Verification After repairs, clear the fault code using Cat ET software and perform a DEF system prime and purge procedure. Monitor live data during a test cycle to confirm proper pump operation and voltage readings within specification (typically 0.5-3.5V during modulation).

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Caterpillar service manual for your specific machine model and serial number. If you're uncomfortable performing electrical diagnostics, contact a certified Caterpillar technician to prevent further damage to emission control components.