• Pilot bearing – two sizes exist on LS cranks. Measure your crank pilot bore or match the bearing you remove.
  • Small‑OD (inner pocket): GM 14061685 / ACDelco CT1078 (OD ≈ 1.094" / 27.8 mm, ID ≈ 0.59" / 15 mm)
  • Large‑OD (outer pocket): GM 12557583 / ACDelco CT1082 (OD ≈ 1.705–1.707" / 43.3 mm, ID ≈ 0.59" / 15 mm)
• Recommended new (one‑time) bolts
  • Flywheel bolts (6): GM 11569956
  • Pressure plate bolts (6): GM 12561465
• “While you’re in there”
  • Concentric slave/throwout bearing: GM 24264180 (+ remote bleeder)
  • Rear main seal: GM 89060436 and rear cover gasket: GM 12639249
  • Clutch kit if worn

• Blind‑hole pilot bearing puller + slide hammer (avoid the grease/bread trick)
• Pilot‑bearing installer/driver, clutch alignment tool (26‑spline T‑56)
• Flywheel holding tool; inch‑lb and ft‑lb torque wrenches
• Lift or stands; transmission jack(s); support the engine (wood pad under pan or support bar)

• Lower the rear cradle slightly and slide the torque‑tube/transaxle assembly rearward a few inches.
• This clears the input shaft from the clutch so you can pull the bellhousing, clutch, and flywheel to reach the pilot bearing.

• Disconnect negative battery cable.
• Raise/support car level. Remove the driveline tunnel closeout panel (re‑torque later: 10 N·m (89 lb‑in)).

• Unplug downstream O₂ sensors; drop mid‑section/H‑pipe as needed.
• Re‑install torques: O₂ sensors 41 N·m (30 lb‑ft); H‑pipe → rear pipe 50 N·m (37 lb‑ft); exhaust hangers 50 N·m (37 lb‑ft).
• Remove H‑pipe hanger → bellhousing fasteners (re‑install 50 N·m (37 lb‑ft)).
• (If needed) Remove starter (50 N·m / 37 lb‑ft) and the flywheel inspection cover (25 N·m / 18 lb‑ft).

• Support the rear transaxle cradle; loosen as needed to lower a few inches.
• Re‑install torques: transaxle mount → bracket nuts 59 N·m (43 lb‑ft); mount → rear crossmember nuts 50 N·m (37 lb‑ft); rear crossmember nuts (use new nuts) 110 N·m (81 lb‑ft).
• Unbolt the concentric slave (leave hydraulic line connected if possible). Re‑install slave bolts 12 N·m (106 lb‑in).
• Unbolt torque tube → engine flywheel housing and slide the torque‑tube/transaxle rearward a few inches. Re‑install those bolts 50 N·m (37 lb‑ft).

• Remove bellhousing (a.k.a. flywheel housing). Re‑install bolts 50 N·m (37 lb‑ft).
• Remove clutch pressure plate & disc (loosen evenly). Re‑install cover bolts 63 N·m (47 lb‑ft) in a star pattern.
• Lock flywheel and remove. Use new flywheel bolts. Re‑install in stages: 15 lb‑ft → 37 lb‑ft → 74 lb‑ft (final). (Blue, medium threadlocker recommended.)

• Use a blind‑hole puller + slide hammer. Do not hydraulic it out with grease/bread.
• Clean/inspect the crank bore; lightly oil the new bearing’s OD.
• Orientation:
  • Small‑OD 14061685: install with the internal seal toward the transmission.
  • Large‑OD 12557583: double‑sealed; orientation not critical.
• Drive the bearing squarely to the shoulder:
  • Inner pocket (small‑OD): flush to pocket shoulder.
  • Outer pocket (large‑OD): fully seated in outer bore.

• Flywheel: clean threads; blue threadlocker; torque in stages 15 → 37 → 74 lb‑ft.
• Clutch: align disc; pressure plate bolts 63 N·m (47 lb‑ft) in a star.
• Bellhousing → engine: 50 N·m (37 lb‑ft).
• Torque tube → bellhousing: 50 N·m (37 lb‑ft).
• Slave cylinder: 12 N·m (106 lb‑in); route/clip line; bleed thoroughly (consider adding a remote bleeder now).
• Mounts & cradle: return ride height; torque hardware as in Step 2.
• Exhaust & closeout: O₂ 41 N·m; H‑pipe → rear 50 N·m; hangers 50 N·m; H‑pipe hanger → bellhousing 50 N·m; tunnel closeout panel 10 N·m.

ENGINE SIDE• Flywheel bolts (6): 15 → 37 → 74 lb‑ft (20 → 50 → 100 N·m)• Pressure plate bolts (6): 47 lb‑ft (63 N·m)• Bellhousing (flywheel housing) → engine: 37 lb‑ft (50 N·m)• Starter bolts: 37 lb‑ft (50 N·m)• Inspection cover bolts: 18 lb‑ft (25 N·m)• Rear main cover bolts (if replaced): 22 lb‑ft (30 N·m) TORQUE TUBE / TRANSAXLE• Torque tube → flywheel housing: 37 lb‑ft (50 N·m)• Concentric slave cylinder (TOB): 106 lb‑in (12 N·m)• Trans mount → bracket nuts: 43 lb‑ft (59 N·m)• Trans mount → rear crossmember nuts: 37 lb‑ft (50 N·m)• Rear crossmember nuts (new nuts): 81 lb‑ft (110 N·m)• Torque‑tube coupler bolts (if disturbed): 52 lb‑ft (70 N·m) EXHAUST / CLOSEOUT• O₂ sensors: 30 lb‑ft (41 N·m)• H‑pipe → rear pipe: 37 lb‑ft (50 N·m)• H‑pipe hanger → bellhousing: 37 lb‑ft (50 N·m)• Driveline tunnel closeout panel: 89 lb‑in (10 N·m)

• Confirm which pilot‑bearing pocket your crank uses (inner ≈ 1.094" OD vs outer ≈ 1.705" OD).
• Small‑OD 14061685 installs with the seal facing the transmission; large‑OD 12557583 is double‑sealed.
• Use a blind‑hole puller (don’t hydraulic the bearing out).
• Bleed the clutch thoroughly if the slave was opened; a remote bleeder is a big quality‑of‑life upgrade on C5s.
• If you disturb the torque‑tube couplers, re‑torque to 70 N·m (52 lb‑ft).

Quote:

Originally Posted by frodo84

The AI engine would go into a continuous loop until it destroyed itself after attempting to reconcile "what is the best oil and oil filter" based on input from this forum.

• Oil: Mobil 1 5W-30 (or any full-synthetic that meets GM4718M) — this is what GM filled the car with and specified for the C5 Z06. 10W-30 is acceptable in ambient temps above 0 °F (-18 °C).
  
  • Capacity: ~6.5 qt with filter.
  • Change interval: Follow the Oil Life Monitor; it will typically call for changes between ~3k–15k miles depending on use.
  • Track/spirited use: Check level frequently; GM advises running the oil about 1 qt above the full mark during competitive driving, then drain back to normal afterward.
• Filter: ACDelco PF44 (GM service part listed for the C5).
  
• Handy specs:
  
  • Drain plug torque: 18 lb-ft (25 N·m).

1) What usually fails & how it shows up

• The Electronic Brake Control Module (EBCM) sits on the Brake Pressure Modulator Valve (BPMV) and runs ABS, Traction Control and (if equipped) Active Handling. When it sees a problem it sets DTCs and asks the cluster to display SERVICE ABS / SERVICE TRACTION / SERVICE ACTIVE HANDLING and an ABS icon. (tuningconcepts.com)
  
• Typical EBCM‑internal failure codes on C5s are C1214 (solenoid valve relay coil/contact circuit open) and C1255 (EBTCM internal malfunction). These codes commonly point to an internal relay or board fault inside the module. (ecutesting.com)
  
• Less often the BPMV/pump or a wheel speed sensor (WSS) is the culprit (those throw different codes). The pump motor is part of the BPMV and is not serviceable separately.
  

2) Tools you’ll want

• An ABS‑capable scan tool (GM Tech 2 or equivalent) – ordinary OBD‑II readers won’t pull EBCM codes/data. GM service info explicitly retrieves C‑codes from the EBCM with a scan tool and notes DTCs don’t clear by battery disconnect; they clear via the scan tool or after ~100 ignition cycles.
  
• A multimeter (ohms/AC mV), basic hand tools, and a T‑20 Torx driver for the EBCM screws. (MotorTrend, absfixer.com)
  

3) Step‑by‑step diagnosis (fast but thorough)

1. Pull the ABS/EBCM codes
   Use the scan tool and write down all current/history C‑codes from the EBCM. GM’s table defines the common ones:
   
   • C1214 – system relay coil/contact circuit open (internal to EBCM).
     
   • C1255 – EBTCM internal malfunction (ABS/TCS disabled).
     
   • C1242/C1243 – BPMV pump motor electrical fault or stalled (points you at the BPMV/pump).
     
   • C1221–C1235 – wheel speed sensor signal/variation/open (points you at a hub/sensor or wiring).
     
2. Power & grounds first
   Low or noisy power will light the dash. Inspect the EBCM connector for terminal fit/corrosion and ensure the EBCM ground is clean and tight (GM has you check this at the very start of diagnosis). On C5s, the “usual suspect” grounds near the front are G101/G102 (by the RH headlamp), G103 (under the brake booster), and G104 (in front of the battery)—clean these to shiny metal and retighten. (CorvSport.com)
   
3. If you have wheel‑speed or “sensor zero” codes
   Jack that corner and test the hub’s sensor at the connector: spec is 850–1350 Ω resistance and >100 mV AC while you spin the wheel. C5 WSS are built into the hub—if it’s out of spec, replace the hub assembly.
   
4. If you have pump/valve codes (C1242/C1243 or solenoid valve circuit)
   These implicate the BPMV/pump or internal EBCM drivers. GM notes the pump is integrated with the BPMV; the solenoid circuits are internal to the EBCM. If power/grounds/connectors check out, you’re down to BPMV vs. EBCM per the flow charts.
   
5. If you have C1214 and/or C1255 (and power/grounds are good)
   That’s the classic EBCM internal failure on C5s. At this point you either:
   
   • Remove and send the EBCM for rebuild, or
     
   • Replace with a rebuilt unit (01–04 are widely serviceable; 97–00 are more limited but some shops do them). (ecutesting.com, UpFix, speedofix.com)
     

4) EBCM removal (no hydraulics opened)

1. Ignition OFF. Disconnect the EBCM harness. Remove the two insulator nuts and lift the EBCM/BPMV just high enough to access the insulator bolt and module screws.
   
2. Remove the insulator mounting bolt from the EBCM.
   
3. Remove the six (6) EBCM‑to‑BPMV T‑20 screws.
   
4. Pull the EBCM straight off the BPMV, don’t tear the seal.
   
5. Reinstall in reverse. Torque the six screws in two passes: 27 in‑lb (3 N·m), then 53 in‑lb (6 N·m). Tighten the front insulator bolt to 10 ft‑lb (14 N·m) and the two insulator nuts to 106 in‑lb (12 N·m).
   

5) Repair options & year differences

• Rebuild your module (2001–2004): Well‑supported, “plug‑and‑play” (no programming) from reputable shops (ABSFixer, UpFix, etc.). Typical symptoms addressed include no‑comm, intermittent power, C1214, C1255; services advertise turnaround and lifetime warranties. (absfixer.com, UpFix)
  
• Rebuild for early cars (1997–2000): Historically harder (some boards are potted), but there are specialists that will repair them now—availability varies. (Examples: SpeedoFix, AutoECU list 97–00 services; confirm your part number and fault codes with the rebuilder before shipping.) (speedofix.com, autoecu.com)
  
• Replace the BPMV (rare): Only if you have pump‑motor faults and the electrical checks point to the BPMV. GM notes the pump is integral to the BPMV.
  
• Part numbers: Common C5 EBCM p/ns seen by rebuilders include 12216561, 10343433, 10323578, 10315150 (varies by year/option). Match numbers when buying cores. (ecutesting.com)
  

6) After reinstall

1. Reconnect, torque as above, and ensure the harness lever is fully latched.
   
2. Turn the key ON (don’t start), then scan and clear DTCs. Per GM, codes don’t reliably clear by battery disconnect.
   
3. Road‑test: straight‑line drive to allow the EBCM self‑test, then varied conditions to verify no new DTCs and normal ABS/Active Handling behavior.
   

7) Quick decision tree

• Wheel‑speed codes (C1221–C1235)? Test hub: 850–1350 Ω, >100 mV AC when spun → replace hub if out of spec.
  
• Pump/relay codes (C1242/C1243, valve driver specific) with good power/grounds? Follow GM tree; pump = BPMV; valve driver = EBCM.
  
• C1214 and/or C1255 after clean power/grounds and good connector → rebuild or replace EBCM.
  

Safety & tips

• Clean G101/G102/G103/G104 grounds whenever you have intermittent ABS/Traction warnings; it’s free and often helps, especially on older C5s. (CorvSport.com)
  
• Count the screws—six on late C5s. Use the GM torque sequence so you don’t warp the case or nick the seal.
  
• Don’t open brake lines unless you’re replacing the BPMV; if you do, you’ll need a scan tool for the Automated ABS Bleed. (tuningconcepts.com)