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SPN 70 — Parking Brake Switch

Updated: 2026-11-14

Do not driveMinutes

J1939 code SPN 70. Below — how the fault is worded at the factory by Ford Trucks, International, KAMAZ-5490, Mercedes-Benz, Renault Trucks and ZF AS-Tronic, and what the second half of the code (FMI) means in the standard.

How to check it yourself

The parking brake switch: it tells the unit whether the pneumatic parking brake is applied. Automatic application and protection against moving with the brake on depend on it.

What it should read

Switch state with the brake applied and releasedchanges with the brake — checked per diagnostics
Parking brake circuit pressureper the manufacturer's manual

Check order

  1. Apply and release the parking brake on a stationary vehicle and watch the switch state in diagnostics.
  2. FMI 2, 13, 19 (unreliable signal, vehicle moving): if in doubt, stop at once; check the switch connector and the adjustment of the parking brake mechanism.
  3. FMI 9, 19 (over CAN, arriving with gaps): see the J1939 bus sections higher up the list — the general methods are the same.
  4. FMI 7 (circuit fault): check the parking brake air system for leaks with soapy water.

Common causes — from most to least frequent

  1. Stuck switch or its oxidised connector.
  2. Leak in the parking brake air system.
  3. Adjustment of the parking brake mechanism.
  4. CAN bus gaps from the brake unit.

InternationalKAMAZ-5490Mercedes-BenzRenault TrucksZF AS-Tronic

International

FMI 2Air Powered Park Brake — The Auto apply portion with the Air Powered Park Brake is not Operating
FMI 7Air Powered Park Brake — Air Powered Park Brake is stuck
FMI 14Air Powered Park Brake — Air Powered Park Brake is stuck; Air Powered Park Brake — The Auto Apply portion with the Air Powered Park Brake is not operating

KAMAZ-5490 (Mercedes, K-line)

FMI is per the block maker's own table, not the J1939 table below.

FMI 9Parking brake switch: CAN message update rate abnormal. K-line code on KamAZ-5490: ADM3 17409.
FMI 19Parking brake switch: erroneous data received over CAN. K-line code on KamAZ-5490: ADM3 17419.

Mercedes-Benz

FMI 2Park Brake Status Not Plausible (Vehicle Moving)
FMI 13J1939 Park Brake Switch Signal from Source CCVS1, CCVS2 or CCVS3 is missing or not available = SNA (signal not available)
FMI 19J1939 Park Brake Switch Signal from Source CCVS1, CCVS2 or CCVS3 is erractic = undefined value but not SNA

Renault Trucks

FMI 6Short to battery positive voltage (internal fault in the Astronic unit). Repair: Switch the ignition off, switch it on again and repeat the test. If the fault persists, replace the control unit.
FMI 7Parking brake circuit fault. Repair: Check the parking brake. Clear the fault codes. If the fault persists, replace the trailer control module.

ZF AS-Tronic gearbox

FMI is per the block maker's own table, not the J1939 table below.

FMI 6Short circuit to positive supply on valve Y6 output (engagement valve).

What FMI means in J1939

SPN 70 FMI 270/2 · 70.2data erratic or intermittent
SPN 70 FMI 670/6 · 70.6current above normal or grounded circuit
SPN 70 FMI 770/7 · 70.7mechanical system not responding
SPN 70 FMI 1370/13 · 70.13calibration out of range
SPN 70 FMI 1470/14 · 70.14manufacturer-specific instructions
SPN 70 FMI 1970/19 · 70.19error in received network data

Can I keep driving

Do not drive. Stop as soon as it’s safe to do so — don’t keep going.

What happens if you keep driving

Time you have: Minutes

Part of the brake circuit or ABS/EBS is out of service. The pedal may still feel normal — until the first emergency stop or descent.

Next comes longer stopping distance, a skid on a slick surface, failure on a long downgrade. This is the case where "I will take it slow" does not work.

What to check on the spot

Let the air system build to working pressure and listen for leaks. Don’t drive with faulty brakes.

Nearby: brakes

Related codes

Makes with this code

Mercedes-BenzRenault TrucksInternationalKAMAZ-5490

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