Network, generic (extended)

U3036 Communication Authentication Signal Performance

Check engine lightOn

EmissionsNot relevant

Drive cycleNot required

Limp modeNo

U3036 judges authentication over time rather than a single bad frame: checks keep failing, cannot be completed, or sender and receiver lose step, for example in their freshness counters. AUTOSAR SecOC shows why this differs from U3035: a receiver retries when no freshness value is available or the crypto service is busy and only gives up after a configured number of build or verify attempts. Ford stores U3036 in the 2023 Super Duty PCM; SSM 51497 explains that it is logged while the PCM keeps monitoring as the CAN bus goes to sleep, and needs no action without other codes, MIL or drivability faults. TSB 23-2421 covers 6.8L and 7.3L trucks with MIL, P061B and U0140, cured by new PCM software. After a TRON module swap Ford also lists U3036 among codes from keys that were not redistributed.

Likely causes

Monitoring software flags authentication during bus sleep or wake-up

Freshness counters of sender and receiver out of step

Keys not redistributed after module replacement

Sending module intermittently missing on the bus

Symptoms

Code stored after a self-test or key-off without complaints
MIL together with P061B or U0140 on some engines
Secured functions working only intermittently

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€0–300

Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

can bussecurity module

Related codes

U3035 U3034 U3033 P061B U0140

References: autosar.org, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.