Use GM's Own Baseline
Chevrolet Performance's LS control-system instructions recommend clean, secure grounds and specifically call for a minimum 3/4-inch braided strap from the engine to the chassis. The same instructions call for a minimum 8-gauge battery feed to the controller fuse-block stud.
Harness Routing Matters
GM also warns to keep the harness away from sharp edges, pinch points, rotating parts and exhaust heat, and to secure/protect unused connectors. Those sound basic, but they are common causes of intermittent swap faults.
| Circuit | Good practice |
|---|---|
| Battery / starter | Large, clean connections sized for cranking current. |
| Engine ground | Direct battery/engine path plus a substantial engine-to-chassis bond. |
| ECM / fuse block | Dedicated fused feeds sized to the harness/controller requirements. |
| Fuel pump / fans | Use relays and fusing sized for actual current; let the ECM command the relay rather than carrying load through a small control wire. |
| Sensors | Do not share noisy high-current grounds with sensitive sensor-reference circuits. |
Diagnosis Order
- Battery state and cranking voltage.
- Voltage drop across positive and ground paths while cranking.
- ECM power and grounds with the circuit loaded.
- 5V reference integrity and sensor plausibility.
- Relay input, control and output — do not replace a relay until you know which side is missing.
Electrical rule: a continuity test with no load is not the same as a voltage-drop test under load. High-resistance grounds often “ohm good” but fail when current rises.
Sources & Further Reading
These links are here so you can verify the numbers and go deeper into the original technical material.