GMC Sierra 1500 Double Cab Electrical Diagnostics & Engine Repair

Advice On Your Quote

1. ECM Update for P2101 Throttle Body Code

• Quoted Labor: $169.95
• Typical Labor: $50–$120 (0.5–1 hour)
• Advice:
  This is a quick “dealer-level” task, basically plugging in a diagnostic computer to update your Engine Control Module. Shops sometimes charge more if they have to pay for the software access, but $170 is pretty steep for this area and job. In our experience, this really shouldn’t be more than $120. I’d gently question the price here—see if they’ll clarify, or get a second opinion at another shop.

2. B1S1 O2 Sensor Replacement

• Quoted Labor: $426.51
• Normal: $200–$300 (Parts $100–$150, Labor $50–$120)
• Advice:
  $426 is definitely on the high end, even with quality parts. Unless this sensor is in a seriously tough spot to access (which is pretty uncommon on your GMC), it shouldn’t be anywhere near this expensive for just the labor. Make sure the quote isn’t including extra parts or “shop supplies.” If not, I’d recommend shopping this around—this could be $150 cheaper at a reputable independent shop.

3. Knock Sensor 2 and Connector Replacement

• Quoted Labor: $530.48
• Normal: $200–$350 (Parts $60–$120, Labor $95–$180)
• Advice:
  Again, this is a bit high unless there’s something unique about your truck that makes access unusually tough (sometimes on certain engines these are under the intake manifold, but even then, $530 seems too much). This doesn’t smell like the usual upsells (like “induction cleanings"), but I’d ask for a breakdown of labor time charged. A fair shop should land closer to $350 all in.

4. Vent Solenoid Replacement

• Quoted Labor: $597.98
• Normal: ~$130 (Parts $36–$103, Labor ~$95)
• Advice:
  $598 for a vent solenoid is way, way over what’s normal. Even if there’s a little extra labor for hard-to-reach spots, you’d have to be dealing with major rust or seized bolts to justify this price. Most shops should land under $150. Unless they’re doing extra emissions or system tests not listed, this is worth questioning—and honestly, I'd seek another quote.

5. Oil Cooler Lines Replacement

• Quoted Labor: $661.40
• Normal: $190–$450 (Parts $50–$150, Labor $140–$300)
• Advice:
  This is the most labor-intensive job on your list. Still, even at the high end, $450 (parts and labor) covers most scenarios. Unless your truck is really rusted or they’re replacing extra hoses not listed here, $661 feels high. I’d get a NAPA or local reputable shop quote—likely to be $200 cheaper.

General Comments

• Are these upsells?
  These aren’t classic “bolt-on” upsells (things like induction cleanings, unnecessary flushes, or fast-wearing wipers). They're legitimate repairs, but they’re all priced high for your area and this vehicle. Nothing stands out as pure unnecessary work here; it just looks like very strong pricing for routine jobs.
• Should you do anything right now?
  If the vehicle runs rough or has Check Engine lights showing, you’ll want to address these jobs—but you can save a lot at an independent shop. If you’re comfortable, you could consider doing things like the O2 sensor or vent solenoid DIY for much less (with the right tools, these are pretty straightforward on a Sierra). But if you're not into wrenching yourself, call around to reputable local shops with your list in hand and see if they can give you better numbers.
• Final point:
  No one likes feeling overcharged. You’re being smart to check. In our experience, a fair total for all this work, parts and labor, should be closer to $800–$1200 lower than what you were quoted. Definitely worth getting a second opinion before saying yes.