Ccc Tbi Tests W/codes: Overview — Chevrolet RV Cutaway G30 (1985-1994)

MODEL IDENTIFICATION

GM Body Code/Series		Applicable Models
"C/K" Series (New Aero-Style) (1)
Chevrolet		Pickup
GMC		Pickup
"M" Series Mini-Vans
Chevrolet		Astro
GMC		Safari
"G" Series Vans
Chevrolet		Van
GMC		Van
"P" Series Vans
Chevrolet		Parcel Van
GMC		Parcel Van
"R/V" Series (Older Style) (2)
Chevrolet		Blazer, Pickup, Suburban
GMC		Jimmy, Pickup, Suburban
"S/T" Series (3)
Chevrolet		S/T Blazer, S10 Pickup
GMC		S/T Jimmy, S15 Pickup
(1) "C" Series is the 2WD version and "K" Series is the 4WD version. (2) "R" Series is the 2WD version and "V" Series is the 4WD version. The "R/V" series was formerly called the C/K" series prior to the release of the redesigned downsized and more aerodynamic) new "C/K" series. (3) "S" Series is the 2WD version and "T" Series is the 4WD version.

(1)	"C" Series is the 2WD version and "K" Series is the 4WD version.

(2)	"R" Series is the 2WD version and "V" Series is the 4WD version. The "R/V" series was formerly called the C/K" series prior to the release of the redesigned downsized and more aerodynamic) new "C/K" series.

(3)	"S" Series is the 2WD version and "T" Series is the 4WD version.

BODY CODE IDENTIFICATION CHART

Test Description

Note. Test numbers refer to test numbers on diagnostic chart.

If fuse in holder is blown, see wiring diagram for Code 54 for complete electrical circuit.
Using a test light connected to 12 volts, probe each system ground circuit to ensure good ground is present. See ECM voltage pin charts for ECM pin locations of ground circuits.

Note. Test numbers refer to test numbers on diagnostic chart.

If there is a problem with ECM that causes a "SCAN" tester to not read Serial Data, then ECM should flash Code 12. If Code 12 does flash, ensure "SCAN" tester is working properly by testing on another vehicle. If "SCAN" tester is functioning properly and circuit No. 461 is okay, the PROM, MEM-CAL, or ECM may be at fault for "NO ALDL" symptom.
If light goes off when ECM connector is disconnected, then circuit No. 419 is not shorted to ground.
This step checks for an open diagnostic circuit No. 451.

Chart A2, No ALDL Data or Won't Flash Code 12, "SES" Light On Steady. Scheme 26

Scheme 26: Chart A2, No ALDL Data or Won't Flash Code 12, "SES" Light On Steady

Note. Test numbers refer to test numbers on diagnostic chart.

"SERVICE ENGINE SOON" light on is basic check for ignition and battery supply to ECM. No "ALDL" may be due to an ECM problem. CHART A2 will diagnose the ECM. If TPS is over 2.5 volts, engine may be in "clear flood" mode, that will cause starting problems. If coolant sensor is below -22°F (-30°C), ECM will provide fuel for extremely cold temperatures that will completely flood engine.
Check voltage at spark plugs with ST-125 (J-26792). No spark indicates basic ignition problem.
While cranking engine, there should be no fuel spray with injector disconnected. Replace injector if it sprays or drips excessively.
Using Injector Test Light (J-34730, BT-8329A), test injector circuit. A blinking light indicates ECM is controlling injector.
This determines if fuel pressure is present at injector and that injector is operating properly.

Note. Test numbers refer to test numbers on diagnostic chart.

"SERVICE ENGINE SOON" light on is basic check for ignition and battery supply to ECM. No "ALDL" may be due to an ECM problem. CHART A2 will diagnose the ECM. If TPS is over 2.5 volts, engine may be in "clear flood" mode, that will cause starting problems. If coolant sensor is below -22°F (-30°C), ECM will provide fuel for extremely cold temperatures that will completely flood engine.
Check voltage at spark plugs with ST-125 (J-26792). No spark indicates basic ignition problem.
While cranking engine, there should be no fuel spray with injector disconnected. Replace injector if it sprays fuel or drips excessively.

Chart A3 Cranks, But Will Not Run (All Except 2.5L). Scheme 27

Scheme 27: Chart A3 Cranks, But Will Not Run (All Except 2.5L)

Note. Test numbers refer to test numbers on diagnostic chart.

These tests will determine if the ignition module is generating a reference pulse, if wiring is at fault or if ECM is at fault. Touch and connect a 12-volt test light to circuit No. 430, a reference pulse should be generated. If injector test light blinks, ECM and wiring are okay.
This tests for 12 volts to injector. It will also determine if there is a short to voltage on ECM side of circuit.
This tests for continuity to ECM.

Chart A4, Injector Circuit Diagnosis (2.5L). Scheme 28

Scheme 28: Chart A4, Injector Circuit Diagnosis (2.5L)

Note. Test numbers refer to test numbers on diagnostic chart.

These tests will determine if the ignition module is generating a reference pulse, if wiring is at fault or if ECM is at fault. Touch and connect a 12-volt test light to circuit No. 430, a reference pulse should be generated. If injector test light blinks, ECM and wiring are okay.
This tests for 12 volts to injector. It will also determine if there is a short to voltage on ECM side of circuit.
This tests for continuity to ECM.

Chart A4, Injector Circuit Diagnosis (All Other Models). Scheme 29

Scheme 29: Chart A4, Injector Circuit Diagnosis (All Other Models)

Note. Test numbers refer to test numbers on diagnostic chart.

Fuel pump is activated if circuit No. 120 wiring is okay. If pump runs, problem may be located in fuel pump relay circuit. The following steps will locate this problem.
Next 2 steps check for power and ground circuits to fuel pump relay.
This determines if ECM can control the fuel pump relay.
Oil pressure switch serves as back-up for fuel pump relay to help prevent a "NO START CONDITION". If fuel pump relay was found to be inoperative, oil pressure switch circuit should also be tested to determine why it did not operate fuel pump.

Chart A5, Fuel Pump Relay Ckt Diagnosis ("M" & "S/T" Series). Scheme 30

Scheme 30: Chart A5, Fuel Pump Relay Ckt Diagnosis ("M" & "S/T" Series)

Note. Test numbers refer to test numbers on diagnostic chart.

Fuel pump is activated if circuit No. 120 wiring is okay. If pump runs, problem may be located in fuel pump relay circuit. The following steps will locate this problem.
Next 2 steps check for power and ground circuits to fuel pump relay.
This determines if ECM can control the fuel pump relay.
Oil pressure switch serves as back-up for fuel pump relay to help prevent a "NO START CONDITION". If fuel pump relay was found to be inoperative, oil pressure switch circuit should also be tested to determine why it did not operate fuel pump.

Note. Test numbers refer to test numbers on diagnostic chart.

Pressure is present, but is less than 9 psi (.63 kg/cm 2 ), fall into 2 categories: Regulated Pressure, But Less Than 9 PSI (.63 kg/cm 2 ) Amount of fuel delivered to injector is adequate, but pressure is too low. System will run lean and may set Code 44. Also, hard starting cold and poor overall performance may result. Restricted Flow Causing Pressure Drop Normally, a vehicle with fuel pressure of less than 9 psi (.63 kg/cm 2 ) at idle will not be driveable. However, if the pressure drop occurs only while driving, engine will normally surge, then stop as pressure begins to drop rapidly.
Restricting fuel return line allows fuel pump to develop maximum pressure (dead head pressure). When battery voltage is applied to pump test terminal, pressure should be 13-18 psi (.91-1.27 kg/cm 2 ).
This determines if high fuel pressure is due to restricted fuel return line or a faulty pressure regulator on throttle body unit.

Note. Test numbers refer to test numbers on diagnostic chart.

Code 13 will set under the following conditions: Engine at normal operating temperature. At least 2 minutes of operation after engine starts. Oxygen sensor voltage signal steady between .35 and .55 volt. Throttle position sensor signal above 4%. All of these conditions must be sustained for about one minute. If conditions for Code 13 exist, system will not go into "Closed Loop" mode of operation.
This determines if sensor is at fault, or if wiring or ECM is cause of Code 13.
Use only a high impedance digital volt/ohmmeter. Test checks continuity of circuit No. 412 and circuit No. 413. If circuit No. 413 is open, ECM voltage on circuit No. 412 will be over .6 volt (600 millivolts).

Note. Test numbers refer to test numbers on diagnostic chart.

Code 14 will set if signal voltage indicates coolant temperature above 266°F (130°C) for more than three seconds.
Tests if circuit No. 410 is shorted to ground. This will cause conditions for Code 14.

Note. Test numbers refer to test numbers on diagnostic charts.

Code 15 will set if signal voltage indicates coolant temperature of less than -47°F (-44°C) than three seconds.
Test simulates Code 14. If ECM recognizes low signal voltage, (high temperature) and "SCAN" tester reads 266°F6 (130°C) or above, ECM and wiring are all okay.
Test will determine if circuit No. 410 is open. There should be 5 volts present at sensor connector if measured with DVOM.

Note. Test numbers refer to test numbers on diagnostic chart.

Code 21 will set under the following conditions: Engine running. TPS signal voltage greater than about 3.5 volts. All conditions must be present for at least 5 seconds. TPS signal voltage over 4.5 volts with ignition on, engine off. With throttle closed, TPS should read less than .70 volt. If not, check adjustment (if applicable).
With TPS disconnected, TPS voltage should go low if ECM and wiring are okay.
Probing circuit No. 452 with a test light checks 5-volt signal return circuit. Faulty 5-volt return circuit will cause a Code 21.

Note. Test numbers refer to test numbers on diagnostic chart.

Code 22 will set when engine is running and TPS signal voltage is less than about .2 volt for 3 seconds.
Simulates Code 21 (high voltage). If ECM recognizes high signal voltage, ECM and wiring are okay.
TPS adjustment (2.8L engine only). With throttle closed, TPS voltage reading should be .42-.54 volt.
This simulates high signal voltage to check for open in circuit No. 417.

Note. Test numbers refer to test numbers on diagnostic chart.

Code 23 will be set if the following conditions are met: Signal voltage indicates manifold air temperature below -22°F 30°C) for 12 seconds. Time since engine start is one minute or longer. No vehicle speed sensor reading (vehicle stationary).
A Code 23 will set due to an open sensor, wire, or connection. This test will determine if wiring and ECM are okay.
This determines if signal circuit No. 472 or the 5-volt return circuit (No. 452) is open.

Note. Test numbers refer to test numbers on diagnostic chart.

Code 24 will set if the following conditions exist for at least 3 seconds

Circuit No. 437 voltage is constant.
Engine speed is 900-4400 RPM.
Less than 2% throttle opening.
Low load condition (low airflow).
Transmission not in Park or Neutral.

The above conditions are met during a road load deceleration.

This monitors ECM voltage on circuit No. 437. With wheels turning, pulsing action will result in varying voltage. Variation will be greater at low wheel speeds to an average of 4-6 volts at about 20 MPH.
A voltage of less than one volt at ECM connector indicates that circuit No. 437 is shorted to ground. Disconnect circuit No. 437 at VSS. If voltage now reads above 10 volts, VSS is faulty. If voltage remains less than 10 volts, circuit No. 437 wire is grounded. If circuit No. 437 is not grounded, check for faulty ECM connector or ECM.
A steady 8-12 volts at ECM connector indicates circuit No. 437 is open or faulty VSS.
This is a normal voltage that indicates a possible intermittent condition.

Note. Test numbers refer to test numbers on diagnostic chart.

Code 25 will be set if the following conditions are met: Signal voltage indicates manifold air temperature below 302°F 150°C) for 2 seconds. Time since engine start is one minute or longer. Vehicle speed sensor reading is present (vehicle moving).

Note. Test numbers refer to test numbers on diagnostic chart.

With ignition on, engine off, solenoid should not be energized and vacuum should not flow to EGR valve. Grounding test terminal will energize the solenoid and vacuum should flow to EGR valve.
Checks for plugged EGR passages. If passages are plugged, engine may have severe detonation on acceleration.
The EGR solenoid will not be energized in Park or Neutral positions. This step will determine if the P/N switch input is being received by the ECM.

Note. Test numbers refer to test numbers on diagnostic chart.

Grounding diagnostic terminal, EGR solenoid should be energized and allow vacuum to be applied to EGR valve and vacuum should hold.
When diagnostic terminal is ungrounded, vacuum to EGR valve should bleed off through a vent in solenoid and valve should close. The gauge may or may not bleed off, this does not indicate a problem.
This test will determine if the electrical control of the system is at fault or if connector or solenoid is at fault.
Negative backpressure valve should hold vacuum when engine is not running.
When engine is started, exhaust backpressure should cause vacuum to bleed off and valve to fully close.

Note. Test numbers refer to test numbers on diagnostic chart.

Code 33 will be set under the following conditions: When signal is too high for more than 6 seconds. Engine misfire or a low, unstable idle. Manifold pressure greater than 22.3 in. Hg with A/C off, or greater than 24 in. Hg with A/C on with engine running. Throttle angle less than 2% with engine running. The above 2 conditions must be present for 2 seconds before ECM will store Code 33.
With MAP sensor disconnected, the ECM should recognize low voltage if ECM and wiring are okay.

Note. Test numbers refer to test numbers on diagnostic chart.

Code 34 will set under the following conditions: Engine running at less than 600 RPM. Manifold pressure is less than 3.8 in. Hg. Above conditions must be present for at least one second. Engine running above 600 RPM. Throttle angle greater than 20%. Manifold pressure greater than 3.8 in. Hg. Above conditions must be present for at least one second.
Tests to see if sensor is cause of low voltage, or if it is an ECM fault, or wiring problem.
Simulates high signal voltage to check for an open in circuit No. 432. If test light is bright during test, circuit No. 432 is probably shorted to ground. If "SCAN" tester reads over 4 volts, circuit No. 416 can be checked for open or short to ground by measuring voltage at terminal "C" (should be 5 volts).

Note. Test numbers refer to test numbers on diagnostic chart.

Continue with test even if engine will not idle. If idle is too low, "SCAN" will display 80 or more counts or steps. If idle is high, "SCAN" will display zero counts (steps). Occasionally an erratic or unstable idle may occur. Engine speed may vary 200 RPM or more up and down. Disconnect IAC. If condition is unchanged, IAC is not at fault. There is a system problem. Proceed to step 3).
When engine was stopped, IAC valve retracted (more air) to fixed park position to provide increased airflow during next engine start. "SCAN" will display 100 or more counts.
IAC MUST be disconnected before performing this step. Test light will confirm ECM signals by a steady or flashing light on all circuits.
There is a remote possibility that one of the circuits is shorted to voltage that would have been indicated by a steady light. Disconnect ECM and turn ignition on. Probe terminals to check for this condition.

Note. Test numbers refer to test numbers on diagnostic chart.

Code 42 means the ECM has seen an open, or short to ground, in EST or by-pass circuit. This confirms Code 42, and confirms that fault causing the code is also present.
Checks for normal EST ground path through ignition module. An EST circuit No. 423 shorted to ground will also read less than 500 ohms (will be checked later).
As test light voltage touches circuit No. 424, module should switch, causing ohmmeter to "overrange" if meter is in the 100-200 ohms position. Selecting 10-20,000 ohms position will indicate above 5000 ohms. The important thing is that the module "switched".
The module did not switch and this step checks for: EST circuit No. 423 shorted to ground. By-pass circuit No. 424 open. Faulty ignition module connection or module.
Confirms that Code 42 is a faulty ECM and not an intermittent in circuit No. 423 or circuit No. 424.

Note. Test numbers refer to test numbers on diagnostic chart.

If conditions for Code 43 are present, "SCAN" will display "YES". There should not be a knock at idle unless an internal engine problem, or system problem, exists.
This determines if system is functioning at this time. Usually knock signal can be generated by tapping on right exhaust manifold. If no knock signal is generated, try tapping on block close to sensor.
Because Code 43 sets when signal voltage on circuit No. 485 remains low, this step should cause the signal on circuit No. 485 to go high. The 12-volt signal should be seen by ECM as "no knock", if ECM and wiring are okay.
This determines if knock signal is being detected on circuit No. 496, or if ESC module is defective.
If circuit No. 496 is routed too close to secondary ignition wires, ESC module may see the interference as a knock signal.
This checks ground circuit to ESC module. An open ground will cause voltage on circuit No. 485 to be about 12 volts. This would cause Code 43 functional test to fail.
Connecting circuit No. 496 with test light to 12 volts should generate a knock signal. This will determine if ESC module is operating properly.

Note. Test numbers refer to test numbers on diagnostic chart.

Code 44 is set when the O2 sensor signal on circuit No. 412 remains below .2 volt for 20 seconds, and the system is operating in "Closed Loop".

Note. Test numbers refer to test numbers on diagnostic chart.

Code 45 is set when the O2 signal on circuit No. 412 remains below .7 volts for 50 seconds, the system is operating in "Closed Loop", time since engine start has been one minute or longer, and throttle angle is greater than 2% (about .2 volt above idle voltage).

Note. Test numbers refer to test numbers on diagnostic chart.

Check MAP sensor output voltage to ECM. This voltage, without engine running, represents a barometric reading to the ECM.
Apply 10 in. Hg vacuum to MAP sensor should cause voltage to be about 1.2 volts less than voltage in step 1). Upon applying vacuum to sensor, the change in voltage should be immediate. A slow voltage change indicates a faulty sensor.
Check vacuum hose to sensor for leaks or restriction. Be sure no other vacuum devices are connected to MAP hose.

MAP Output Check Flow Chart & Schematic. Scheme 31

Scheme 31: MAP Output Check Flow Chart & Schematic

MAP Output Check. Scheme 32

Scheme 32: MAP Output Check

Note. Test numbers refer to test numbers on diagnostic chart.

Checks for closed switch to ground in Park position. Different makes of "SCAN" testers will read P/N signal differently. Refer to tester's instruction manual for type of display used for specific tester.
Checks for an open switch in Drive or Reverse.
Be sure "SCAN" tester indicates Drive, even while wiggling shifter, to test for an intermittent or misadjusted switch in Drive.

Note. Test numbers refer to test numbers on diagnostic chart.

Checks for normal (cranking) voltage to terminal "C9" of ECM. Test light should be on during cranking and then go off when engine is running.
Checks to determine if source of open fuse or fuse link was a faulty ECM.

Crank Signal Diagnosis - Flow Chart & Schematic. Scheme 33

Scheme 33: Crank Signal Diagnosis - Flow Chart & Schematic

Crank Signal Diagnosis. Scheme 34

Scheme 34: Crank Signal Diagnosis

Note. Test numbers refer to test numbers on diagnostic chart.

Checks for ECM signal voltage on circuit No. 495, and confirms ground circuit No. 450 is okay.
Maximum resistance, or infinity, indicates an open switch.
Less than one ohm indicates that switch is closed when power steering pressure is high. Switch is okay.

Note. Test numbers refer to test numbers on diagnostic chart.

Checks for low refrigerant as cause for no A/C.
This and following tests check for faulty A/C control relay.

A/C Clutch Control Diagnosis Flow Chart (2.5L) (1 of 3). Scheme 35

Scheme 35: A/C Clutch Control Diagnosis Flow Chart (2.5L) (1 of 3)

A/C Clutch Control Diagnosis. Scheme 36

Scheme 36: A/C Clutch Control Diagnosis

A/C Clutch Control Diagnosis Schematic (2.5L) (2 of 3). Scheme 37

Scheme 37: A/C Clutch Control Diagnosis Schematic (2.5L) (2 of 3)

Note. Test numbers refer to test numbers on diagnostic chart.

Checks for faulty cycling switch. Solenoids and relays are turned on and off by the ECM, using internal electronic switches (drivers). Each driver is part of a group of 4, called"Quad-Drivers". Failure of one driver can damage any other driver in set.
Solenoid and relay coil resistance must measure more than 20 ohms. Less resistance will cause early failure of ECM driver. Using an ohmmeter, check coil resistance of A/C relay before replacing ECM.

Note. Test numbers refer to test numbers on diagnostic chart.

Checks for low refrigerant as cause for no A/C.
This and following tests check for faulty A/C control relay.

A/C Clutch Control Diagnosis Flow Chart (2.8L) (1 Of 3). Scheme 38

Scheme 38: A/C Clutch Control Diagnosis Flow Chart (2.8L) (1 Of 3)

A/C Clutch Control Diagnosis. Scheme 39

Scheme 39: A/C Clutch Control Diagnosis

A/C Clutch Control Diagnosis Schematic (2.8L) (2 of 3). Scheme 40

Scheme 40: A/C Clutch Control Diagnosis Schematic (2.8L) (2 of 3)

Note. Test numbers refer to test numbers on diagnostic chart.

Checks for faulty cycling switch. Solenoids and relays are turned on and off by the ECM, using internal electronic switches (drivers). Each driver is part of a group of 4, called "Quad-Drivers". Failure of one driver can damage any other driver in set.

Solenoid and relay coil resistance must measure more than 20 ohms. Less resistance will cause early failure of ECM driver. Using an ohmmeter, check coil resistance of A/C relay before replacing ECM.

Circuit Test Description

Turning on A/C supplies battery voltage to circuit No. 59 A/C compressor clutch, and to terminal "B8" of ECM connector to increase idle air rate and maintain idle speed.

The ECM does not control the A/C compressor clutch; therefore, if A/C does not function, service A/C system.

If A/C is operating properly and idle speed dips too low when A/C compressor turns on, or flares too high when A/C compressor turns off, check for an open circuit No. 59 to ECM. If circuit is okay, it is a faulty ECM connector terminal "B8" or ECM.

A/C On Signal Diagnosis (4.3L, 5.0L, 5.7L, 7.4L Engines) - Flow Chart & Schematic. Scheme 41

Scheme 41: A/C On Signal Diagnosis (4.3L, 5.0L, 5.7L, 7.4L Engines) - Flow Chart & Schematic

Note. Test numbers refer to test numbers on diagnostic chart.

Continue with test even if engine will not idle. If idle is too low, "SCAN" will display 80 or more counts (steps). Occasionally an erratic or unstable idle may occur. Engine speed may vary 200 RPM or more up and down. Disconnect IAC. If condition is unchanged, IAC is not at fault. There is a system problem. Proceed to step 3).
When engine was stopped, IAC valve retracted (more air) to fixed park position to provide increased airflow during next engine start. "SCAN" will display 100 or more counts.
IAC MUST be disconnected before performing this step. Test light will confirm ECM signals by a steady or flashing light on all circuits.
There is a remote possibility that one of the circuits is shorted to voltage that would have been indicated by a steady light. Disconnect ECM and turn ignition on. Probe terminals to check for this condition.

Note. Test numbers refer to test numbers on diagnostic chart.

1) Two wires are checked to ensure that an open is not present in a spark plug wire.
1A) If spark occurs with 4-terminal distributor connector disconnected, pick-up coil output is too low for EST operation.
2) A spark indicates the problem must be distributor cap or rotor.
3) Normally, there should be battery voltage at "C" and "+" terminals. Low voltage would indicate an open or a high resistance circuit from distributor to coil or ignition switch. If "C" terminal voltage was low, but "+" terminal voltage is 10 volts or more, circuit from "C" terminal to ignition coil, or ignition coil primary winding, is open.
4) Checks for a shorted module or grounded circuit from ignition coil to module. Distributor module should be turned "Off", so normal voltage should be about 12 volts. If module is turned "ON", voltage would be low, but above one volt. This could cause ignition coil failure from excessive heat. With open ignition coil primary winding, small amount of voltage will leak through module from "Bat" terminal to "Tach" terminal.
5) Applying 1.5-8 volts to module terminal "P" should turn module "ON" and "Tach" terminal voltage should drop to about 7-9 volts. This test will determine whether the module or coil is faulty, or if pick-up coil is not generating proper signal to turn module "ON". This test can be performed by using a DC battery with a rating of 1.5-8 volts. The use of the test light is mainly to allow the "P" terminal to be probed more easily. Some digital multimeters can also be used to trigger the module by selecting ohms, usually the diode position. In this position, the meter may have a voltage across its terminals which can be used to trigger the module. The voltage in the ohms position can be checked by using a second meter, or by checking the manufacturer's specification of the tester being used.
6) This should turn module "OFF" and cause a spark. If no spark occurs, fault is most likely in ignition coil because most module problems would have been found before this point in the procedure. A Module Tester (J-24642) could determine which is at fault.

Note. Test numbers refer to test numbers on diagnostic chart.

1) Two wires are checked to ensure that an open is not present in a spark plug wire.
1A) If spark occurs with 4-terminal distributor connector disconnected, pick-up coil output is too low for EST operation.
2) A spark indicates the problem must be distributor cap or rotor.
3) Normally, there should be battery voltage at "C" and "+" terminals. Low voltage would indicate an open or a high resistance circuit from distributor to coil or ignition switch. If "C" terminal voltage was low, but "+" terminal voltage is 10 volts or more, circuit from "C" terminal to ignition coil, or ignition coil primary winding, is open.
4) Checks for shorted module or grounded circuit from ignition coil to module. Distributor module should be turned "OFF", so normal voltage should be about 12 volts. If module is turned "ON", voltage would be low, but above one volt. This could cause ignition coil failure from excessive heat. With open ignition coil primary winding, small amount of voltage will leak through module from "Bat" terminal to "Tach" terminal.
5) Checks for open module, or circuit to module. Applying 12 volts to "P" terminal or module should turn module "ON" and voltage should drop to about 7-9 volts.
6) This should turn module "OFF" and cause a spark. If no spark occurs, fault is most likely in ignition coil because most module problems would have been found before this point in the procedure. A Module Tester (J-24642) could determine which is at fault.

Note. Test numbers refer to test numbers on diagnostic chart.

If Code 43 is not set, but a knock signal is indicated with engine running at 1500 RPM, listen for an internal engine noise. Under a no load condition, there should not be any detonation. If knock is indicated under no load condition, an internal engine problem may exist.
Usually a knock signal can be generated by tapping on right exhaust manifold. This test can also be performed at idle. Step 1) was run at 1500 RPM to determine if a constant knock signal was present that would affect engine performance.
Tests whether the knock signal is due to the sensor, a basic engine problem, or the ESC module.
If the module ground circuit is faulty, the ESC module will not function correctly. The test light should light, indicating the ground circuit is okay.
Contacting circuit No. 496 with a test light to 12 volts should generate a knock signal to determine whether the knock sensor is faulty, or if the ESC module cannot recognize a knock signal.

Note. Test numbers refer to test numbers on diagnostic chart.

This is a system performance test. When vehicle goes to "Closed Loop", air will switch from the exhaust ports to divert air to the air cleaner.
Tests for a grounded electric divert circuit. Normal system light will be off.
Checks for an open control circuit. Grounding diagnostic terminal will energize the solenoid. If the ECM and circuits are okay. In this step, if test light is on, circuits are okay and fault is in valve connections or valve.
Checks for voltage from battery through a fuse to the solenoid.

AIR Management Check Flow Chart (Elect. Air Control Valve). Scheme 42

Scheme 42: AIR Management Check Flow Chart (Elect. Air Control Valve)

AIR Management Check Flow Chart (Elect. Air Control Valve). Scheme 43

Scheme 43: AIR Management Check Flow Chart (Elect. Air Control Valve)

AIR Management Check Schematic (Elect. Air Control Valve). Scheme 44

Scheme 44: AIR Management Check Schematic (Elect. Air Control Valve)

Note. Test numbers refer to test numbers on diagnostic chart.

Checks for solenoid being stuck in open position.
Checks for solenoid always being energized.
Grounding test terminal should energize the solenoid, causing vacuum to drop.
Negative backpressure valve should hold vacuum with engine off.
When engine is started, exhaust backpressure should cause vacuum to bleed off, and valve to fully close.

Note. Test numbers refer to test numbers on diagnostic chart.

With ignition on (engine off), the solenoid should not be energized and vacuum should not flow to EGR valve.
Grounding the diagnostic terminal will energize the solenoid and allow vacuum to flow to the EGR valve.
Checks for plugged EGR passages. If passages are plugged, the engine may have severe detonation upon acceleration.
The EGR solenoid will not be energized in Park or Neutral. This test will determine if the P/N switch input is being received by the ECM.

Note. Test numbers refer to test numbers on diagnostic chart.

Check continuity through the brake switch and TCC solenoid.
Check ability of ECM to energize the TCC solenoid. Grounding the diagnostic connector should energize the relay and cause the light to go out.
This test by-passes the TCC solenoid and checks for an open or short in circuit No. 422.

Note. Test numbers refer to test numbers on diagnostic chart.

Glowing test light indicates that battery voltage and continuity through TCC Solenoid are okay.
Checks for vehicle speed sensor (VSS) signal to ECM, using a "SCAN" tester.
Checks for 4th gear signal to ECM. This signal will not prevent TCC engagement, but could cause a change in engage/disengage speed points.

Note. Test numbers refer to test numbers on diagnostic chart.

This should not turn the shift light on. If light is on, there is a short to ground in circuit No. 456 wiring, or a fault in the ECM.
This should turn shift light on.
This check for an open in the shift light circuit, or a faulty ECM.