Ccc Tbi Tests W/codes: Other Chevrolet Sportvan G30

Without "SCAN" Tester

The ECM stores component failure information for the CCC system under a related trouble code which can be recalled for diagnosis and repair. When recalled, these codes will be displayed by flashes of the "SERVICE ENGINE SOON" light. Trouble codes are displayed starting with the lowest numbered code. Only codes that represent a definite malfunction will be shown.

Trouble codes are read by counting flashes of the "SERVICE ENGINE SOON" light, or by reading output on a diagnostic tester ("SCAN" tester) connected to the ALCL connector. These special tools are faster and more accurate, but are not mandatory.

If a "SCAN" tester is not available, read the flashes of the "SERVICE ENGINE SOON" lamp. For example, "FLASH", "FLASH", pause, "FLASH", longer pause, identifies "21". The first flashes are the first digit of the code, second flashes are the second digit.

With "SCAN" Tester

A "SCAN" tester provides a visual reading of most of the ECM inputs and some of the outputs controlled by the ECM. With the "SCAN" tester in the code position, the stored code will be displayed in the display window.

By connecting the "SCAN" tester to the ALDL connector and a 12-volt power supply, valuable information can be received from the CCC system. The technician's knowledge of the system and understanding of the "SCAN" tester's limitations can provide information that would otherwise be difficult to obtain. However, "SCAN" testers cannot replace volt/ohmmeters when called for within diagnostic charts.

The "SCAN" tester can display the following information in the display window

1. "ON" when ECM has commanded A/C clutch into operation. This does not mean that A/C clutch is operating, only that ECM has instructed it to commence operation.
2. "YES" when A/C is activated.
3. Actual battery voltage reading detected at ECM ignition input.
4. "CLOSED LOOP" or "OPEN LOOP", depending upon mode that engine control system is operating under.
5. Diagnostic codes.
6. Coolant temperature in degrees Centigrade.
7. RPM that ECM is trying to maintain at idle.
8. "ON" when ECM has commanded EGR valve to open. This does not mean that EGR valve is open, only that ECM has instructed EGR valve to open to allow EGR flow.
9. Position of EGR valve pintle.
10. "YES" when transmission is in fourth gear.
11. A number that represents the position that the ECM thinks the idle air control valve is in at that time.
12. A number, in milliseconds, that represents the pulse width ("on" time) that the ECM is commanding to the injectors.
13. Amount of spark retard in number of degrees.
14. "YES" when knock is detected or "NO" when knock is not detected.
15. Manifold air temperature in degrees Centigrade.
16. Low voltage when the manifold pressure is low (high vacuum), or high voltage when the pressure is high (low vacuum).
17. Vehicle speed in miles per hour.
18. Oxygen sensor reading ranging from 1 to 999 millivolts. If consistently below 350 millivolts, fuel system is lean; if consistently above 550 millivolts, fuel system is rich.
19. Percent of throttle angle.

These are only some of the capabilities of the "SCAN" tester. Consult "SCAN" tester manufacturer's diagnostic manual for complete explanation of the tester and its limitations.

ECM TROUBLE CODE IDENTIFICATION

System Check

1. If complaint is "SERVICE ENGINE SOON" light related, this check will lead to the most likely problem area (if a malfunction exists). Enter diagnostic mode by grounding terminal "B" of ALDL connector and record stored trouble codes.
2. Begin diagnosis with the lowest numbered code shown and go to the numbered trouble code chart. If code "51" is displayed, see PROM or MEM-CAL removal and installation in this article.

Field Service Mode Check

1. This test confirms proper operation of fuel system and verifies "Closed Loop" operation. Clear codes and perform this test after any repair is completed.
2. When performing this check, always engage parking brake and block drive wheels. On some engines, the oxygen sensor will cool off after only a short period of time while engine is idling.
3. This will cause engine to go into open loop. To restore closed loop mode, run engine at part throttle for several minutes, accelerating from idle to part throttle several times.

Fuel Module Check Procedure

On a 7.4L engine, or a "G" Series Van with a 5.7L engine and all other 5.7L engines over 8,500 GVW, a fuel module will override the ECM two second timer and the fuel pump will run for twenty seconds and the the shut off if the vehicle is not started. This circuit corrects a hot restart (vapor lock) during a high ambient temperature condition.

1. Disconnect fuel module.
2. With a test light and ignition ON, probe from connector terminal C to ground. Circuit is okay if light is ON. Circuit is open if light is OFF.
3. Probe between connector terminals C and D with test light. Circuit is okay if light is ON. There is a open in ground circuit if light is OFF.
4. Turn ignition OFF. Probe between connector terminals A and D with test light. Turn ignition ON. Test light should illuminate for two seconds. If light is OFF, there is an open in the circuit.
5. Replace the fuel module if there is no twenty second fuel pump operation.

Chart A5A, Fuel Pump Relay Schematic ("R/V" W/Dual Tanks). Scheme 153

Chart A5A, Fuel Pump Relay Flow Chart ("R/V" W/Dual Tanks). Scheme 154

From Chart A-3 "Fuel Pump Does Not Run". Scheme 155

On a 7.4L engine, or a "G" Series Van with a 5.7L engine and all other 5.7L engines over 8,500 GVW, a fuel module will override the ECM two second timer and the fuel pump will run for twenty seconds and the the shut off if the vehicle is not started. This circuit corrects a hot restart (vapor lock) during a high ambient temperature condition.

1. Disconnect fuel module.
2. With a test light and ignition ON, probe from connector terminal C to ground. Circuit is okay if light is ON. Circuit is open if light is OFF.
3. Probe between connector terminals C and D with test light. Circuit is okay if light is ON. There is a open in ground circuit if light is OFF.
4. Turn ignition OFF. Probe between connector terminals A and D with test light. Turn ignition ON. Test light should illuminate for two seconds. If light is OFF, there is an open in the circuit.
5. Replace the fuel module if there is no twenty second fuel pump operation.

System Too Lean (High Air/Fuel Ratio)

Idle speed may be too high or too low. Engine speed may vary up and down. Disconnecting IAC does not help. May set Code 44.

"SCAN" and/or voltmeter will read an oxygen sensor output of less than .30 volt (300 millivolts). Check for low regulated fuel pressure, or water contaminated fuel. A lean exhaust with an oxygen sensor output fixed above .80 volt (800 millivolts) indicates a contaminated sensor, usually silicon. This may set a Code 45.

System Too Rich (Low Air/Fuel Ratio)

Idle speed too low. "SCAN" counts usually above 80. System obviously rich, and may exhibit black smoke exhaust.

"SCAN" and/or voltmeter will read an oxygen sensor signal fixed above .80 volt (800 millivolts). Check for high fuel pressure, and/or leaking or sticking injector.

Throttle Body

Remove IAC and inspect bore for foreign material, or evidence of IAC valve dragging in bore.

A/C Compressor Relay Failure

Diagnose A/C system if shorted to ground. If relay is faulty, an idle problem may exist. See ROUGH, UNSTABLE, INCORRECT IDLE, STALLING in the CCC TESTS W/O CODES article in this section.

Code 35, Idle Speed Error (2.5L) Flow Chart & Schematic. Scheme 156

Code 35, Idle Speed Error (2.5L). Scheme 157

O2 Sensor Wire

Sensor pigtail may be mispositioned and contacting exhaust manifold. Check for intermittent ground in wire between connector and sensor.

Fuel Contamination

Water, even in small amounts, near in-tank fuel pump inlet can be delivered to fuel injectors. Water causes a lean exhaust and can set Code 44.

Fuel Pressure

System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving the vehicle at various road speeds and/or loads to confirm. See CHART A6.

AIR System

Be sure air is not being directed to exhaust ports while in "Closed Loop". If block learn value goes down while squeezing air hose to left side of exhaust ports, service AIR management system. If okay, oxygen sensor is faulty.

Circuit No. 413

If circuit No. 413 is open, voltage at terminal "D7" will be over one volt.

System will go rich if pressure is too high. The ECM can compensate for some increase. However, if pressure is too high, Code 45 may be set. See Chart A6 for fuel pressure. See CHART A4 for leaking injector. Check for fuel contaminated oil.

HEI Shielding

An open ground circuit may result in interference, or induced electrical "noise". The ECM looks at this "noise" as a reference pulse. The additional reference pulse results in higher than actual engine speed signal. The ECM then delivers too much fuel, causing the system to go rich. Engine tachometer will also show higher than actual engine speed which can help in diagnosing this problem.

Canister Purge

Check for fuel saturation. If full of fuel, check canister control and hoses.

MAP Sensor

An output that causes the ECM to receive a higher than normal manifold pressure (low vacuum) can cause the system to go rich. Disconnecting the MAP sensor will allow the ECM to set a fixed value for the MAP reading. Substitute a different MAP sensor if the rich condition is gone while the MAP sensor is disconnected.

Pressure Regulator

Check for leaking fuel pressure regulator diaphragm by checking for presence of liquid fuel in vacuum line to regulator.

TPS

An intermittent TPS output will cause the system to go rich, due to a false indication of engine acceleration.

Code 45, Rich Exhaust Indication Flow Chart & Schematic. Scheme 158

Code 45, Rich Exhaust Indication. Scheme 159

CODE 51 - FAULTY MEM-CAL (2.5L)

Check that all pins are fully inserted into socket. If okay, replace MEM-CAL, clear memory and recheck. If Code 51 reappears, replace ECM.

CODE 51 - PROM PROBLEM (2.8L/4.3L/5.0L/5.7L/7.4L)

Check that all pins are fully inserted in socket. If okay, replace PROM, clear memory and recheck. If Code 51 appears, replace ECM.

CODE 52 - FUEL CALPAK MISSING (2.8L/4.3L/5.0L/5.7L/7.4L)

Check for missing CALPAK and that all pins are fully inserted into socket. If okay, replace ECM.

CODE 53 - SYSTEM OVER VOLTAGE (2.5L)

This code indicates a basic alternator problem. Code 53 will be set if voltage at ECM terminal "B1" is greater than 17.1 volts for 2 seconds. Check and repair charging system.

CODE 55 - ECM PROBLEM (2.8L/4.3L/5.0L/7.4L)

Be sure ECM grounds are okay and that MEM-CAL, PROM, and/or CALPAK are properly latched. If okay, replace ECM. Clear codes, confirm "Closed Loop" operation, and no "SERVICE ENGINE SOON" light.

Idle speed may be too high or too low. Engine speed may vary up and down. Disconnecting IAC does not help. May set Code 44.

"SCAN" and/or voltmeter will read an oxygen sensor output of less than .30 volt (300 millivolts). Check for low regulated fuel pressure, or water contaminated fuel. A lean exhaust with an oxygen sensor output fixed above .80 volt (800 millivolts) indicates a contaminated sensor, usually silicon. This may set a Code 45.

Idle speed too low. "SCAN" counts usually above 80. System obviously rich, and may exhibit Black smoke exhaust.

"SCAN" and/or voltmeter will read an oxygen sensor signal fixed above .80 volt (800 millivolts). Check for high fuel pressure, and/or leaking or sticking injector.

Remove IAC and inspect bore for foreign material, or evidence of IAC valve dragging in bore.

A/C Compressor Or Relay Failure

Diagnose A/C system if shorted to ground. If relay is faulty, an idle problem may exist. See ROUGH, UNSTABLE, INCORRECT IDLE, STALLING in the CCC TESTS W/O CODES article in this section.

IDLE SPEED ERROR FLOW CHART (2.8L, 4.3L, 5.0L, 5.7L & 7.4L ENGINES)

Note. "Scan" Tool Must Be In Open Mode During This Check

Idle Speed Error. Scheme 160

Idle Speed Error Schematic (2.8L, 4.3L, 5.0L, 5.7L & 7.4L Engines). Scheme 161