U0688 code meaning
Lost Communication With Throttle Position Sensor/Switch G
Network system Generic code U06xx codes Check engine light
What U0688 means
Throttle sensor G is the second track of a second throttle body. GM's 23OBDG07 and 24OBDG07 tables, for a program with one throttle per bank, use it for throttle position sensor 2 on bank 2. Both tracks of that throttle travel in one SENT stream, so GM sets U0688 together with U0608 (sensor 1, bank 2) when the line carries no signal, pulse widths fall outside their window or the calibration pulse is off, within 0.13 s and MIL in one trip. NXP's KMA215 shows why: its dual throttle format packs the angle and its inverted copy into a single frame. Raw value checks of track G are P212C under 0.195 V and P212D over 4.805 V, P212B checks synchronisation. Bank 2's throttle can then no longer be positioned reliably, so power is reduced.
U0688 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0688
- Check engine light on the first trip
- Reduced power, uneven running between banks
- U0608 stored at the same time
Common causes of U0688
- Most likelySENT, supply or ground wire to the bank 2 throttle body faulty
- PossibleThrottle body connector loose, wet or corroded
- PossibleSensor electronics in the throttle body failed (replaced as a unit)
- Less likelyEngine controller SENT input fault
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Throttle position sensor gVehicle bus wiring
What each part of U0688 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 88 | The exact fault in that area. |
What to do next
- Note U0688 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0688
What does U0688 mean?
U0688 means "Lost Communication With Throttle Position Sensor/Switch G". Throttle sensor G is the second track of a second throttle body. It is a generic code, so it means the same on every make.
Is it safe to drive with U0688?
Drive gently and only to a workshop. With U0688 the car can go into limp mode (reduced power) to protect itself.
Will U0688 fail an emissions test?
Yes, it can. U0688 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U0688 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U0688 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.