Powertrain, generic · Transmission

P0803 Upshift/Skip Shift Solenoid Control Circuit

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 in the shifter housing that, at light load and low speed blocks the way from 1st into 2nd and 3rd so the driver shifts 1 to 4 – a measure for fuel economy ratings; the 1-4 lamp (P0804) shows it. P0803 means the solenoid control circuit is open. GM's tables check the low-side driver while it is off: too low a voltage or over 200 kΩ to ground, with at least 9 V and over 250 rpm, 5 of 6 samples of 250 ms (2019 LT5: 20 of 25), type B with the MIL after two trips; shorts are P080C and P080D. An open circuit leaves the solenoid unpowered, so 1 to 2 always works. 'Skip-shift eliminators' with the wrong resistance are a frequent cause.

Likely causes

Solenoid unplugged or replaced by a skip-shift eliminator with the wrong resistance
Connector at the gearbox loose or corroded
Solenoid coil open
Harness damaged
Engine module driver faulty

Symptoms

  • Check engine lamp after two trips
  • 1-4 lockout no longer works (1-2 always possible)
  • Otherwise no change in driving

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–250
Time0.5–2 h

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

Parts involved

skip shift solenoidsolenoid wiringengine control module

Related codes

P0804P080BP080CP080DP0801

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, en.wikipedia.org.