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U0654 Lost Communication With Diesel Intake Air Flow A Position Sensor

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Diesel intake air flow valve A is the throttle ahead of the intake manifold: it creates the vacuum for high EGR rates, trims airflow for filter regeneration and shuts at switch-off. GM's 2025 diesel tables 25OBDG04A and 25OBDG04B read its angle by SENT and set U0654 when the data stop refreshing for more than 6.25 ms while the line is stuck low or high, a frame is faulty, or the counters freeze. 04A needs 200 of 250 checks, 04B 480 of 600, both every 6.25 ms after cranking with over 11 V at the relay. Type A means MIL in the first trip. GM evaluates the out-of-range codes P02E8 and P02E9 only while no such link fault exists. Ford's 2023 diesels monitor the same throttle with P02E8/P02E9 and do not list U0654. Sensor B has U0655.

Likely causes

Oil, soot or corrosion in the throttle body connector
SENT signal, supply or ground wire damaged
Position sensor in the throttle unit failed (usually replaced with the unit)
Engine controller SENT input fault

Symptoms

  • MIL in the first trip
  • EGR control restricted, particulate filter regeneration delayed
  • Engine may shake more at switch-off

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–700
Time0.5–2.5 h

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

Parts involved

diesel intake airflow position sensor avehicle bus wiring

Related codes

U0655P02E0P02E1P02E6P02E7P02E8P02E9P02EA

References: gsi.ext.gm.com, gsi.ext.gm.com, fordservicecontent.com, law.cornell.edu.