SERVICE MANUAL NUMBER 23
FUEL INJECTION SYSTEM TROUBLESHOOTING
Page 5D-3
90-861326--1 MARCH 1999
Diagnostic Trouble Codes for the MEFI 3 454 cid (7.4L) / 502 cid (8.2L) Engines
Code
Number
Connection
Conditions
Comments
14
ECT high
Minimum run time (10 sec)
Sensor output high (cold) > 240
counts
Open circuit
Faulty sensor
15
ECT low
Minimum run time (10 sec) sensor
Sensor output low (hot) < 7 counts
Short circuit
Faulty sensor
21
TPS high
Sensor output high (> 250 counts)
anytime or, skewed high ( > 70) @
< 700 rpm and < 70 kpa for at least
5 seconds
Open circuit,
WOT Faulty sensor
No reference
ground
22
TPS low
Sensor output low (< 4 counts)
anytime
Short circuit
Faulty sensor
No reference
voltage
23
MAT high
Minimum run time (10 sec)
Sensor output high (cold) > 253
counts
Open circuit
Faulty sensor
25
MAT low
Minimum run time (10 sec) sensor
Sensor output low (hot) < 7 counts
Short circuit
Faulty sensor
33
MAP high
kpa > 80 and tps < 5% and rpm >
500 for at least 5 seconds
Open circuit
Faulty sensor
No Reference
ground
34
MAP low
kpa < 14 and tps > 5% and rpm
<300 for at least 0.5 seconds
Short circuit
Faulty sensor
No reference
voltage
41
EST open (GM
distributor only)
Ignore first 20 spark events requires
10 faults to set code
Open circuit
Faulty ignition
module
42
EST grounded
Ignore first 20 spark events requires
10 faults to set code
Short circuit
Faulty reference
pickup
43
Continuous
knock
Must have continuous knock retard
for at least 30 seconds
Incorrect base
timing
Faulty knock sensor
44
No knock
After 513 tdc knock free events, rpm
> 3000 and MAP > 70 and filtered
sensor noise < 0.14 volts
Disconnected
sensor
Broken/open circuit
Faulty knock sensor
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