Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC U1016: Lost Communications With Engine Controls System
2000 Saturn LS2 AutomaticSECTION DTC U1016: Lost Communications With Engine Controls System
NOTE:
Applies to 4-cylinder models only.
- Perform VEHICLE ON-BOARD DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM. If vehicle on-board diagnostic system check has been performed, go to next step.
- Turn ignition on. Using scan tool, attempt to establish communications with PCM. If scan tool communicates with PCM, problem is intermittent. If engine does not start, check for open battery voltage or ignition voltage circuit to PCM from CONTROLS B+ and/or CONTROLS IGN 1 fuses (10-amp), located in underhood fuse block. If engine starts and runs normally, check for an open in ignition voltage circuit to PCM from IGN 0 fuse (10-amp), located in underhood fuse block. If scan tool does not communicate with PCM, go to next step.
- Turn ignition off for 10 seconds. Turn ignition on and listen for fuel pump or fuel pump relay operation. If fuel pump or fuel pump relay energize for 2 seconds and then turn off, go to next step. If fuel pump or fuel pump relay do not energize for 2 seconds and then turn off, go to step 6.
- Turn ignition off. Disconnect Blue 80-pin PCM connector J1. Using a DVOM, measure resistance between Data Link Connector (DLC) terminal No. 2 and PCM harness connector J1 terminals No. 58 and 59. See Fig 1 and Fig 2 . If resistance is 2 ohms or more, go to next step. If resistance is less than 2 ohms, check for poor connection to PCM. Repair as necessary and retest operation. If PCM connection checks okay, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. Retest operation.
- Check and repair open in class-2 serial data links (Purple wire) between DLC and BCM, instrument panel cluster and PCM, or BCM and PCM. See WIRING DIAGRAMS .
- Check CONTROLS B+ fuse (10-amp), located in underhood fuse block. If fuse is okay, go to next step. If fuse is blown, replace and retest. If fuse blows again, repair short to ground in Orange wire between Blue 80-pin PCM connector J1 terminal No. 20 and CONTROLS B+ fuse. See WIRING DIAGRAMS . Retest operation.
- Turn ignition off. Disconnect Blue 80-pin PCM connector J1. Turn ignition on. Using a DVOM, measure voltage between ground and PCM connector J1 terminal No. 20 (Orange wire). See Fig 2. If battery voltage is present, go to next step. If battery voltage is not present, repair open in Orange wire between Blue 80-pin PCM connector terminal No. 20 and CONTROLS B+ fuse. See WIRING DIAGRAMS . Retest operation.
- Using a DVOM, measure resistance of Black/White wires between left front ground splice pack and PCM harness connector J1 terminals No. 18 and 60, and PCM harness connector J2 terminal No. 64. If any resistance is 2 ohms or more, repair open in affected ground circuit to PCM, or in ground to left front ground splice pack. See WIRING DIAGRAMS . Retest operation. If all resistances are less than 2 ohms, check connections at PCM. If all connections are okay, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. See WIRING DIAGRAMS . Retest operation.
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.