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SPN 802 — Diagonal Circuit Relay 1

Safe to driveTo the nearest safe stop

J1939 code SPN 802. Below — how the fault is worded at the factory by Bendix ABS/ESP, Renault Trucks and WABCO ABS/ESC, and what the second half of the code (FMI) means in the standard.

Bendix ABS/ESPRenault TrucksWABCO ABS/ESC

Bendix ABS/ESP

FMI 3PMV Common Shorted to Voltage
FMI 4PMV Common Shorted to Ground

Renault Trucks

FMI 2Short circuit on the EBS unit power outputs, or lost ground on part of the ABS unit functions. Repair: Check the module inlet and outlet for air leaks. Trailer module X3/3, X3/6, X3/9, X3/12. Front module X3/2, X3/5, X3/8, X3/11. Rear module (axles) X4/2, X4/8, X4/11, X4/14. Rear module (axle) X4/4, X4/7, X4/10, X4/13. If the fault persists, replace the EBS unit. Check the continuity of the ABS unit wiring (X1/10, X1/11, X1/12). If the fault persists, replace the ABS unit.
FMI 3Lost ground on part of the ABS unit functions (with ASR), or the unit ground shorted (without ASR). Repair: Check the continuity of the ABS unit wiring (X1/10, X1/11, X1/12). Check the continuity of the ABS unit wiring (X1/10, X1/11, X1/12). If the fault persists, replace the ABS unit.
FMI 4ABS unit: some functions faulty on the ground side (with ASR fitted). Repair: Check the continuity of the ABS unit wiring (X1/10, X1/11, X1/12). If the fault persists, replace the ABS unit.
FMI 12ABS unit internal fault. Repair: Replace the ABS unit.

WABCO ABS/ESC

FMI 4Supply Voltage is too Low
FMI 5ECU Central Ground Open Circuit
FMI 7Internal Voltage Supply

What FMI means in J1939

SPN 802 FMI 2802/2 · 802.2data erratic or intermittent
SPN 802 FMI 3802/3 · 802.3voltage above normal or shorted high
SPN 802 FMI 4802/4 · 802.4voltage below normal or shorted to ground
SPN 802 FMI 5802/5 · 802.5current below normal or open circuit
SPN 802 FMI 7802/7 · 802.7mechanical system not responding
SPN 802 FMI 12802/12 · 802.12faulty device or component

Can I keep driving

Safe to drive. Below — how much time you have and what happens if you keep going.

What happens if you keep driving

Time you have: To the nearest safe stop

The electrical system is not holding voltage. While the engine runs the alternator carries it; shut it off and you may not restart.

Next the lights go, then modules start dropping out and false codes appear all over the truck. Get to somewhere with help without shutting the engine down.

What to check on the spot

Check the battery terminals and earth strap — corrosion and loose clamps throw false codes all over the truck. Running voltage should be 27–29 V.

Nearby: power supply

Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.