At key-on engine-off, voltage should read 4.3-4.6V indicating barometric pressure (approximately 100 kPa at sea level). At warm idle in park, voltage drops to 0.9-1.4V indicating 20-35 kPa vacuum with visible rhythmic pulsations of 0.1-0.3V amplitude at half engine speed frequency due to intake pulses. Voltage response should be instantaneous during throttle changes.

At idle with engine fully warmed, MAF signal should be stable at 0.7-1.1V with less than 0.05V ripple, corresponding to 3-7 g/s airflow. During throttle snap from idle to 3000 RPM, voltage should rise smoothly without steps or hesitation to 2.5-3.5V, then return smoothly to idle voltage without overshoot or oscillation.

Clean square wave with 12V supply dropping sharply to near 0V when injector energizes, pulse width of 1.5-3.5ms at idle in closed loop. Turn-off produces sharp inductive spike to 50-80V with 2-4 damped oscillations lasting 0.5-1ms before returning to 12V baseline, indicating proper pintle closure.

Clean square dwell period of 2-4ms at idle with battery voltage dropping cleanly to near 0V, followed by sharp inductive kick to 200-350V lasting 1-2ms with 3-5 damped oscillations. Current limiting should show flat bottom during dwell period indicating proper coil saturation.

Firing line should reach 8-15kV at idle with clean vertical rise in under 0.1ms, spark line burns flat and stable at 2-4kV for approximately 1.2ms duration, followed by 4-6 diminishing oscillations. All 8 cylinders should show consistent firing voltage within 3kV of each other.

Traditional narrowband zirconia sensor that monitors catalyst efficiency by showing a stabilized voltage range of 0.6-0.85V during steady-state cruise with very slow gentle transitions (10+ second periods). A healthy catalyst stores oxygen causing downstream sensor to show minimal activity compared to rapid upstream switching. Signal should remain relatively flat with small lazy movements, never rapidly switching like upstream sensor.

Wideband air-fuel sensor (not traditional narrowband) outputs proportional voltage to ECM: approximately 1.5-1.8V during closed-loop at idle representing stoichiometric mixture, swings to 0.8-1.2V during deceleration fuel cut (lean), and 2.5-3.5V during acceleration enrichment (rich). Voltage changes should be smooth and responsive within 100-200 milliseconds of throttle input, with sensor actively controlling fuel trim to maintain target AFR.

Clean digital square wave switching between approximately 0.2V (low) and 11.5V (high) with sharp rise and fall times under 1 microsecond. At idle, expect 4 pulses per cam revolution with equal on/off times creating precise 50% duty cycle for each lobe detection, frequency doubles proportionally with engine RPM.

Clean AC sine wave with 58 evenly-spaced pulses per crankshaft revolution, approximately 3-4V peak-to-peak at idle (600-650 RPM) increasing proportionally with engine speed. Signal should be symmetrical above and below zero volts with no DC offset, showing smooth transitions without noise or dropouts.

Dual redundant analog voltage signals that move in opposite directions providing cross-check validation. At closed throttle (idle), TPS1 reads 0.5-0.9V while TPS2 reads 4.0-4.5V. As throttle opens to wide-open-throttle (WOT), TPS1 rises smoothly to 4.2-4.7V while TPS2 falls to 0.4-0.9V. Combined voltage should always equal approximately 5V, transitions must be smooth without steps or jumps.

At 10-15 mph, expect clean sine waves of 0.5-1.5V peak-to-peak with 10-20 Hz frequency. At 60 mph, amplitude should increase to 5-10V peak-to-peak with proportionally higher frequency. All four sensors should show similar waveforms at the same vehicle speed. Waveform should be symmetrical above and below zero with consistent amplitude.

Clean square wave with sharp transitions between 0V and battery voltage (12-14V). At 10 mph, expect approximately 5-8 Hz frequency. At 60 mph, frequency increases to 30-50 Hz. Duty cycle should be approximately 50% with consistent on/off times. Signal should have fast rise and fall times (under 1ms) with no ringing or oscillation.

At cold start (70°F), expect 2.8-3.2V. As engine warms to operating temperature (195-220°F), voltage should smoothly decrease to 0.45-0.65V. The transition should be gradual with no sudden jumps or dropouts. At full operating temperature, voltage should remain stable with minimal fluctuation.

At ambient temperature of 70°F, expect 2.5-3.0V. Voltage decreases as intake air warms from engine heat or forced induction heating. Signal should be stable with minimal noise. Under hard acceleration or extended idle, voltage may drop to 1.5-2.5V as air warms.

2016 Chevrolet Silverado 1500 Waveform References

Airflow Sensors

Fuel System

Ignition System

Oxygen Sensors

Position Sensors

Speed Sensors

Temperature Sensors