Powertrain, generic · Transmission

P080C Upshift/Skip Shift Solenoid Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

GM's skip-shift (CAGS) on manual gearboxes such as the T56 and TR6060 uses an engine-module solenoid that, at light load, blocks the way from 1st into 2nd so the driver shifts 1 to 4; the 1-4 lamp shows it (P0804). The engine module drives the solenoid with a low-side driver; P0803 is the open circuit. P080C means the control line is shorted to ground: with the driver off it should sit at battery voltage through the coil but reads low (GM: 0.5 Ω or less to ground). GM checks it from 9 V (2015/16: 11–32 V) and above 250 rpm, 5 of 6 samples of 250 ms, type B with the MIL after two trips; the 2019 LT5 uses 20 of 25 samples and type A, one trip. In the 2015/16 tables P080C also covers an open circuit. A low-side short keeps the solenoid energized, so the lockout may stay active.

Likely causes

Control wire chafed through to ground at gearbox or frame
Solenoid coil shorted to its housing
Connector corroded or water ingress
Older GM modules: circuit open or solenoid unplugged
Engine module driver faulty

Symptoms

  • Check engine lamp
  • 1-4 lockout permanently active or not working
  • 1-4 lamp possibly unrelated to the lockout

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–300
Time0.5–2.5 h

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

Parts involved

skip shift solenoidsolenoid wiringengine control module

Related codes

P0803P080BP080DP0804P0801

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.