The COGENG 342-3063 (3423063) Main Harness is a high-grade OEM replacement wiring loom designed specifically for the Caterpillar 336D Excavator powered by the C9 Engine.
As the Main Harness, this is the most critical electrical component in the machine. It is the direct connection between the ADEM A4 ECM (Engine Control Module) and the engine's vital organs:
Fuel Injectors (HEUI system)
Crank & Cam Position Sensors
Turbocharger Actuator
EGR Valve & Intake Throttle
Engine Oil Pressure & Coolant Temperature Sensors
Rail Pressure & Fuel Temperature Sensors
Note: Do not confuse this Main Harness with the Chassis Harness (366-9320) or the External Boom Harness (291-7590). The 342-3063 is the harness that physically wraps around the engine block.
Why choose COGENG 342-3063?
OEM Quality: Manufactured to CAT factory specifications.
Plug-and-Play: No cutting, splicing, or crimping required.
Durable: Resistant to high under-hood temperatures (up to 125°C) and vibration.
Available Now: In stock for immediate global dispatch.
| Parameter | Specification |
|---|---|
| Part Number | 342-3063 |
| Alternate Number | 3423063 |
| Application | CAT 336D / 336D L / 336D LN |
| Engine Type | Caterpillar C9 ACERT (9.3L) |
| ECM Type | ADEM A4 (70-pin + 120-pin connectors) |
| Connector Type | Deutsch, AMP, TE, and CAT proprietary grey plugs |
| Insulation | Cross-linked Polyethylene (XLPE) / TPE |
| Wire Gauge | 0.5mm² (signal) to 5.0mm² (injector/power) |
| Operating Temp | -40°C to +125°C |
| Harness Length | ~4 – 5 meters (engine loop) |
| Packaging | PP bag + Carton box |
This harness is specific to the 336D series with the C9 engine.
| Model | Engine | Compatible Harness |
|---|---|---|
| CAT 336D | C9 ACERT | 342-3063 |
| CAT 336D L | C9 ACERT | 342-3063 |
| CAT 336D LN | C9 ACERT | 342-3063 |
| CAT 336E | C9.3 | Not compatible |
| CAT 336F | C9.3 | Not compatible |
| CAT 336C | *C-9* | Different pinout |
✅ Direct OEM Replacement for:
CAT Part Number: 342-3063 (or 3423063).
Also replaces: 344-6734, 349-2473 (later revisions – check S/N).
⚠️ Critical Verification Check:
Machine Serial Number: Please confirm your machine serial number prefix (e.g., GDC, J2C, K3C, M2D, JLG).
ECM Type: This harness fits the ADEM A4 ECM. If your 336D has an A3 ECM (very early models), please verify before ordering.
Injector Orientation: This loom is configured for the C9 HEUI system.
Step-by-Step Guide for replacing the 342-3063 Main Harness:
Safety First: Disconnect batteries (both, negative first) and allow 5 minutes for ECM discharge.
Documentation: Take photos of the old harness routing.
Remove Old Harness:
Unplug the 70-pin and 120-pin connectors from the ECM.
Disconnect injectors, sensors, and actuators.
Remove the metal retention clips.
Install New Harness:
Start by plugging in the ECM connectors first (ensure they click and lock).
Route the injector sub-harness along the valve cover.
Connect the crank/cam sensors and rail pressure sensor.
Connect the VGT actuator and EGR valve.
Securing: Use zip ties to secure the harness away from moving parts (belts, fan).
Testing: Reconnect batteries. Turn key to "ON" (do not start). Use CAT ET to check for active codes before starting. Start engine and verify no oil/fuel leaks at sensor bases.
Q1: What is the difference between the Main Harness (342-3063) and the External Harness?
A: The Main Harness (342-3063) connects the ECM to the engine block. The External Harness runs on the boom/stick for lights and sensors. They are not interchangeable.
Q2: My 336D is a Tier 4 model with a C9.3 engine. Will this fit?
A: No. Tier 4 C9.3 engines use a different ECM pinout and injector system. This harness is strictly for Tier 3 / Stage IIIA C9 engines.
Q3: Why does my new harness have a different colored wire than my old CAT harness?
A: Wire colors may vary slightly due to supply chain standards, but the function and pinout (location in the connector) remain exactly the same.
Q4: Do I need CAT ET to install this harness?
A: Yes, highly recommended. After replacing the main harness, you should use CAT Electronic Technician to clear old diagnostic codes and calibrate the injector/rail pressure systems.
Q5: Is the 342-3063 a genuine CAT part?
A: No. This is a COGENG aftermarket part. We manufacture it to OEM specifications (ISO9001 certified) as a cost-effective replacement.
Q6: Does this harness include the ECM?
A: No. This is the wiring harness only. It does not include the ECM or sensors.
Q7: How quickly will it ship?
A: We have 500+ pieces in stock. Orders placed before 2 PM ship the same day.
| Parameter | Value |
|---|---|
| Total Conductor Count | 60+ wires |
| Number of Branches | 18-22 branches |
| Connector Sealing | IP67 (Waterproof) |
| Main Fuse Rating | 60A (Main ECM feed) |
| Injector Current | Up to 8A per injector |
Ordering Information
✅ In Stock – Ready to Ship.
✅ MOQ 1 piece accepted for trial orders.
📞 Contact COGENG supplier today to place your order!
*Shipping Details Delivery Return*
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Merchant Return Policy:
Products shipped are not eligible for return or exchange.
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