Auto diagnostics in Chico CA. $199.99/hr written report. HC test $199.99, EVAP $199.99, AC R-1234yf $324.99, electrical $199.99. ASE Master Tech. (530) 826-4275.
Root-cause diagnosis before any repair recommendation. Free code scan with every service. Paid diagnostic = written report of exact failure. HC test $199.99 · EVAP $199.99 · Electrical $199.99 · AC R-1234yf $324.99.
Diagnostics at Tedious Auto Repair in Chico is $199.99/hour. The first hour produces a written report of the root cause or what was tested and eliminated. Flat-fee exceptions: HC combustion test $199.99, EVAP smoke test $199.99, electrical diagnostic $199.99, AC R-1234yf $324.99, coolant pressure test $179.99. Diagnostic fees are never waived or credited to repair. Free code scan (code pull only) with every service. By Buddy Rausch, Owner / ASE Master Technician · Reviewed May 20, 2026
| Service | Price | What You Get |
|---|---|---|
| General Diagnostic CEL, drivability, noise, vibration, stall, no-start | $199.99/hr | Written root-cause report. Additional hours at $199.99/hr with approval. |
| HC Combustion Gas Test Head gasket status — non-invasive | $199.99 flat | Confirms or rules out combustion gases in coolant before teardown. |
| Coolant Pressure Test External leak location | $179.99 flat | Pressurizes system, locates all external leaks. Written report. |
| EVAP Smoke Test Evaporative emission leak | $199.99 flat | Smoke introduced into EVAP system. All leak locations documented. |
| Electrical Diagnostic No-start, parasitic drain, module fault | $199.99 flat | Full electrical trace with written pinpoint test results. |
| AC Diagnostic — R-1234yf 2017+ vehicles | $324.99 flat | Electronic leak detection, pressure test, component verification. |
| Free Code Scan With any service | FREE | Code pull only — not a diagnostic. Shows fault codes, not root cause. |
| Pre-Purchase Inspection Before buying a used vehicle | $199.99 | 100-point + HC test + full OBD scan + written report with estimates. |
Diagnostic fees are never waived or credited toward repair cost. Additional diagnostic hours billed at $199.99/hr with customer approval at each step.
A code scan (or "full scan") reads the fault codes stored in every module: ECM, TCM, ABS, airbag, body control. It tells you which systems have stored faults and what the codes are. It does NOT tell you which component failed or why. Free with every service at Tedious Auto Repair.
A diagnostic is a root-cause investigation. After reading codes, the technician performs pinpoint tests: checking sensor voltage, activating actuators, performing cylinder contribution tests, applying back-pressure tests, performing fuel trim analysis. The diagnostic finds the exact failed component — not just the system it affects.
Example: P0420 (catalyst efficiency) could be a failing catalytic converter, a bad upstream O2 sensor giving false data, an exhaust leak before the sensor, or a coolant leak contaminating the sensor. A code pull gives you P0420. A diagnostic tells you which of these is actually the problem.
Waiving the diagnostic fee to "close the sale" creates an incentive to skip thorough diagnosis and replace the most likely part. At Tedious Auto Repair, you pay for the diagnostic and receive a written report. The repair is a separate decision. This structure ensures we diagnose correctly the first time — not guess and replace.
A flashing CEL means an active misfire severe enough to damage the catalytic converter in real time. Do not drive. Have the vehicle towed or drive directly to us at low RPM. Misfires causing converter damage are an emergency — the longer you drive, the more expensive the repair.
Solid CEL is less urgent than flashing but still requires diagnosis. It could be anything from a loose gas cap to an oxygen sensor to a catalytic converter issue. Don't ignore it — many solid CEL faults worsen over time and become more expensive if deferred.
Resetting the CEL without fixing the root cause causes the light to come back within one drive cycle. Worse: a reset clears readiness monitors — the vehicle fails smog inspection for 5–8 drive cycles while monitors re-run. Fix the cause first, then reset.
Rough running, P030X codes, flashing CEL. Caused by failed spark plugs, ignition coils, fuel injectors, or low compression. Cylinder contribution test identifies which cylinder. Component test identifies what failed.
Rod knock, carbon knock (pre-ignition), or piston slap — each has a different cause and fix. Carbon knock is common on GDI engines in Chico's valley driving. Rod knock requires immediate attention.
Engine misfire, worn motor mounts, or drivetrain issue. We separate engine-origin vibration from drivetrain-origin with targeted tests before recommending any parts.
Vacuum leak, dirty throttle body, failing idle air control valve, bad MAF sensor, or misfire at idle. Diagnosed with live data analysis — not parts replacement guesswork.
Fuel delivery, crankshaft position sensor, throttle body, or torque converter lockup fault. Stalls at idle vs stalls at speed vs stalls when hot each point to different systems.
White smoke = coolant (head gasket). Blue smoke = oil burning. Black smoke = running rich (fuel). Each has a distinct diagnostic path. We start with the least invasive test for each.
2695 CA-32, Chico · (530) 826-4275
$199.99/hour. The first hour delivers a written report identifying the root cause or what was tested and eliminated. Additional hours billed at $199.99/hr with your approval at each step. Flat-fee exceptions: HC combustion test $199.99, coolant pressure test $179.99, EVAP smoke test $199.99, electrical diagnostic $199.99, AC R-1234yf $324.99.
No — never. Diagnostic fees are not credited to repair, not waived, and not free with repair. You pay for the diagnostic and receive a written report. This is non-negotiable — it's how we ensure quality diagnosis before any repair.
A scan (code pull) is free with any service — it reads fault codes stored in the ECM. A diagnostic is a paid root-cause investigation: testing components, verifying sensor data, applying voltage, performing pinpoint tests to find exactly what failed and why. Codes point toward a system; diagnosis finds the exact failed part.
Yes. A flashing CEL means an active misfire severe enough to damage the catalytic converter — do not drive. We diagnose the misfire source: spark plugs, ignition coils, fuel injectors, or compression. Misfires are diagnosed and repaired same-day on most vehicles.
Yes. EVAP smoke test $199.99 flat fee. We introduce low-pressure smoke into the EVAP system and inspect every component — charcoal canister, purge valve, vent solenoid, hoses, and fuel cap — for smoke emergence. Written report of all leak locations.
100-point digital inspection with photos, full OBD scan of all modules, HC combustion test for head gasket status, coolant pressure test, brake inspection, tire measurement, suspension check, fluid condition, and written report with repair estimates. Best $199.99 you'll spend before buying a used car.
$199.99/hr · Written report · Never waived · ASE Master Tech · Open 7 days
📍 2695 CA-32, Chico, CA 95973 · Open Mon–Fri 7AM · Sat 8AM · Sun 9AM — Close 5PM · Open 7 Days
2695 CA-32, Chico · (530) 826-4275
2695 CA-32, Chico · (530) 826-4275 · Cummins · Duramax · PowerStroke
Buddy Rausch founded Tedious Auto Repair in Chico, CA in 2007 and has been serving Butte County for 18+ years. As an ASE Master Technician, Buddy personally oversees diagnostics and quality control on every vehicle. All content on this page reflects real procedures, OEM specifications, and cases seen in the shop. About Buddy Rausch, ASE Master Tech →
Buddy Rausch founded Tedious Auto Repair in Chico, CA in 2007. ASE Master Certified. 18+ years serving Butte County. About Buddy Rausch