Pontiac Fiero 1988 Service Manual page 471

6E2-A-16 DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI)
ECM
PNK/BLK 439
BLU 467 —
W16
- IGN
W1
PNK
—
IGN
BLK/RED 453
PPL/WHT 430
TAN/BLK 424
WHT 423
B16
B9
W19
W6
SECONDARY PRIMARY
WINDING
WHT 121
4-30-87
DIRECT IGNITION
SYSTEM MODULE
TO I.P
V-
OR TACH '
ECM
-/
INJECTOR
DRIVER
GROUND
REFERENCE
BY-PASS
EST
7S 3586
6 26-86
CHART A-3
(Page 2 of 3)
ENGINE CRANKS BUT WON'T RUN
2.5L "P" SERIES (TBI)
Circuit Description:
A magnetic crank sensor is used to determine engine crankshaft position, much the same way as the pick-up
coil did in HEI type systems. The sensor is mounted in the block, near a slotted wheel on the crankshaft. The
rotation of the wheel creates a flux change in the sensor, which produces a voltage signal. The "DIS"
ignition
module then processes this signal and creates the reference pulses needed by the ECM and the signal triggers the
correct coil at the correct time.
If the "Scan" tool did not indicate cranking rpm, and there is no spark present at the plugs, the problem lies in
the Direct Ignition System or the power and ground supplies to the module.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Because the Direct Ignition System uses two plugs
and wires to complete the circuit of each coil, the
opposite spark plug wire should be left connected.
2. This test will determine if the 12 volt supply and a
good ground is available at the "DIS" ignition
module.
3. This test will determine if the ignition module is
not generating the reference pulse, or if the wiring
or ECM are at fault. By touching and removing a
test light to 12 volts on CTK 430, a reference pulse
should be generated. If rpm is indicated, the ECM
and wiring are OK.
4. This test will determine if the ignition module is
not triggering the problem coil, or if the tested coil
is at fault. This test could, also, be performed by
using another known good coil.
The secondary coil winding may be checked by
using a DVM across the coil towers. Resistance
readings should be 5000-10,000 ohms. There
should not be any continuity between either coil
tower and ground.
5. Checks for continuity of the crank sensor and
connections, as well as sensor magnetism.