Engine Running Test

Verify that engine is at normal operating temperature. Run engine at 2000 RPM for 2 minutes. Turn key off and immediately restart engine. Observe voltmeter and vacuum gauge for initialization pulses after restarting engine. Throttle kicker should come on (engine speed increases) at this time and remain on throughout test.
To test knock sensor, have steel bar (socket extension) and 4 oz. hammer ready. As soon as 4 initialization pulses appear, hold steel bar against manifold near knock sensor. Tap bar lightly with hammer for 15 seconds.
NOTE: If voltmeter and vacuum gauge do not pulse, or show steady high or low readings, see NO SELF-TEST OUTPUT.

NOTE: If more than 4 initialization pulses appear, check for open circuit between coil and MCU connector Pin No. 8.
Observe and record service codes. When codes are complete (about 90 seconds), throttle kicker will retract. Stop engine, remove test equipment and reconnect PCV valve. Perform tests for codes in the order that codes were displayed.

NOTE: When code 11 (code 62 for vehicles above 4000 ft.) is displayed for vehicles with a drive complaint of detonation (at WOT only) and/or poor performance, and vehicle is equipped with a universal ignition module, perform SPARK KNOCK TEST. On all other vehicles, testing is complete and MCU is functioning.

MCU DIAGNOSTIC TEST CODES

Code

System Component

1-1

Continue QUICK TEST

1-1 & 6-2 ⁽¹⁾

Barometric Pressure Switch

1-2

RPM Out of Range

2-5

Knock Sensor

4-1

Lean Fuel Mixture

4-2

Rich Fuel Mixture

4-4

Thermactor System

4-5

Thermactor Air Upstream

4-6

Air Not By-passing

5-3 & 5-4

Temperature Switch Open

5-1 & 5-5

Open "Zone Vacuum" Switch

6-1 & 6-5

Closed "Zone Vacuum" Switch

⁽¹⁾	Code 1-1 above 4000 ft. of elevation. Code 6-2 below 4000 ft. of elevation.