MODEL IDENTIFICATION
Vehicle model is identified by fifth character of Vehicle Identification Number (VIN). VIN is stamped on metal pad on top of left end of instrument panel, near windshield. See MODEL IDENTIFICATION table.
| Series (1) | Model |
|---|---|
| "A" & "B" | Aztek |
| "C" & "K" | Cab & Chassis, Sierra, Silverado, Suburban, Tahoe, Yukon & Yukon XL |
| "G" | Chevy Express, Cutaway, RV Cutaway & Savana |
| "L" & "M" | Astro & Safari |
| "S" & "T" | Blazer, Bravada, Jimmy, Sonoma & S10 Pickup |
| "U" | Montana, Silhouette & Venture |
| (1) Vehicle series is fifth character of VIN. | |
| (1) | Vehicle series is fifth character of VIN. |
MODEL IDENTIFICATION
ENGINE MECHANICAL
Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.
VALVE CLEARANCE
Note. All engines are equipped with hydraulic lifters, except for 6.6L diesel engine. Adjustments are not required. The 6.6L diesel engine is equipped with mechanical roller lifters. Adjustment is not required as routine service. Adjustment is only performed after disassembly of engine components. See 6.6L V8 DIESEL in ENGINES.
IGNITION TIMING (GASOLINE)
Note. On all models, ignition timing is controlled by control module and is not adjustable.
CAMSHAFT RETARD OFFSET (5.0L & 5.7L)
Note. Distributor can be adjusted to prevent crossfire.
Inspection
Note. Camshaft retard offset reading will not be accurate with engine speed less than 1000 RPM.
- With ignition off, connect scan tool to Data Link Connector (DLC). Start engine and allow it to reach normal operating temperature.
- Increase engine speed to more than 1000 RPM. Using scan tool, monitor CAM RETARD OFFSET. If camshaft retard indicates zero degrees, distributor is properly adjusted. Procedure is complete. If camshaft retard is not zero degrees, see «ADJUSTMENT»(/chevrolet/blazer/s15-1998-2005/remont/adjustments/#engine-controls-on-vehicle-adjustments) .
- Turn ignition off. Slightly loosen distributor hold-down bolt. Start engine. Increase engine speed to more than 1000 RPM.
- Using scan tool, monitor CAM RETARD OFFSET. To adjust for a negative reading, rotate distributor counterclockwise. To adjust for a positive reading, rotate distributor clockwise.
- Continue to adjust as necessary until zero degrees is attained. Turn ignition off. Tighten distributor hold-down bolt to 18 ft. lbs. (24 N.m). Start engine. Increase engine speed to more than 1000 RPM. Using scan tool, verify camshaft retard offset adjustment.
INJECTION PUMP TIMING/TDC OFFSET (DIESEL)
Note. Injection pump timing is not adjustable on 6.6L diesel.
INJECTION PUMP TIMING (6.5L DIESEL)
Original factory injection pump timing is usually marked with a static timing mark (a line scribed across both the pump mounting flange and front cover). This static timing mark should be used as a reference. If timing mark is not present on mounting flange, scribe a line to assist in how far injection pump needs to be rotated. To check and adjust injection timing, perform the following procedure.
- Start engine and allow it to reach normal operating temperature. Connect scan tool to Data Link Connector (DLC). Set scan tool to OUTPUT TEST/INJ PUMP mode. Activate TDC TIME SET. The DES INJ TIME value will read zero. NOTE: If engine stalls when TDC TIME SET is activated, turn engine off. Loosen injection pump nuts. Slightly rotate injection pump toward driver's side of vehicle. Tighten injection pump nuts. Repeat step 1 .
- With engine running at idle, ensure ACT INJ TIME displays 3.5 degrees. If timing needs adjustment, turn engine off. Adjust injection pump. A .039" (1.0 mm) pump movement equals about a 2 degree timing change.
TDC OFFSET LEARN PROCEDURE (6.5L DIESEL)
This procedure is only used when one of the following conditions exist
- DTC P1214 is set.
- Engine has been replaced.
- Front engine cover has been replaced.
- PCM and injection pump have been replaced.
- CKP sensor has been replaced.
- Start engine and allow it to reach normal operating temperature. Connect scan tool to Data Link Connector (DLC). Clear all DTCs. Turn ignition on, with engine off. Using scan tool, select OUTPUT TEST/INJ PUMP mode. Activate TDC OFFSET LEARN.
- If learned TDC OFFSET reading is between -.25 and -.75 degree, procedure is complete. If reading is not as specified, hold accelerator pedal in wide open throttle position for at least 45 seconds. Turn ignition off for 30 seconds. Start engine. TDC OFFSET reading should be zero. If reading is not zero, repeat step 1 .
- With engine running, PCM will learn new TDC OFFSET when normal operating temperature is obtained and engine speed is less than 1500 RPM. New TDC OFFSET will overwrite previous reading. If new learned TDC OFFSET reading is not between -.25 and -.75 degree, turn ignition off.
- Slightly rotate injection pump and repeat step 1 . A .039" (1.0 mm) pump movement equals about a 2 degree timing change. To achieve a positive reading, rotate pump toward driver's side. To achieve a negative reading, rotate pump toward passenger's side.
GASOLINE ENGINES
Note. DO NOT attempt to adjust idle mixture and idle speed. Both are controlled by Powertrain Control Module (PCM). Incorrect idle speeds are normally caused by dirty throttle plate or vacuum leaks. Ensure all vacuum components are functioning properly.
DIESEL ENGINES
Note. Diesel engines are equipped with electronic fuel injection in which PCM controls all fuel delivery modes based on inputs from APP, ECT and BARO sensors. Idle speed is not adjustable.
Note. Throttle position sensors are not adjustable.
DIESEL ENGINES & 8.1L GAS ENGINE
Throttle control is electronic with no mechanical link from engine to accelerator pedal. PCM monitors position of accelerator pedal based on signals from a nonadjustable Accelerator Pedal Position (APP) module. APP module is mounted above accelerator pedal.
See also:
• MODEL IDENTIFICATION