C5 Tach Dosen't work...
Thread Starter
Cruising
Joined: Jun 2019
Posts: 11
Likes: 0
From: Milton, WI
C5 Tach Dosen't work...
I've got a 2000 Corvette just bought it, it had a lot of little things wrong with it. I'm slowly fixing them. My tach does not read my RPM's. When the key is turned on the tach and speedo both cycle the whole range of the gauge,, when started the tach does nothing. also my heads up display doesn't work either. Any help would be Awesome!!! Thanks
Tech Contributor
Joined: Dec 1999
Posts: 32,910
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The very first thing I would do is read and post the DTCs using the C5 Built in DTC reading routine. Post up what you have. If DTCs don't prove anything concrete, You have to figure out where you are losing the actual TAC Signal.
Most All of the IPC gages are emulated. They don't actually connect to any specific sensor, So, the TAC signal comes from the PCM, goes through the BCM and sends out the signal through the Class 2 serial data line. It has power and works because it sweeps. The issue is the PCM isn't communicating that signal to the IPC through the class 2 data line.
Read and post the DTCs.. That may tell a story to help fix it.
BC
Most All of the IPC gages are emulated. They don't actually connect to any specific sensor, So, the TAC signal comes from the PCM, goes through the BCM and sends out the signal through the Class 2 serial data line. It has power and works because it sweeps. The issue is the PCM isn't communicating that signal to the IPC through the class 2 data line.
Read and post the DTCs.. That may tell a story to help fix it.
BC
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Race Director
Joined: Apr 2007
Posts: 11,152
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From: South Western Ontario
The tach and speedometer are driven by PWM outputs from the PCM, not via the serial bus.
It's a white wire goes from A17 on the PCM to pin 10 of connector 2. It passes through the underhood electrical center in at pin A3 and out at pin D4.
You could check it with a volt meter set to DC. If it is working, the voltage would be low at idle and go up as the rpm's go up. Probably something like 0-10V.
It's a white wire goes from A17 on the PCM to pin 10 of connector 2. It passes through the underhood electrical center in at pin A3 and out at pin D4.
You could check it with a volt meter set to DC. If it is working, the voltage would be low at idle and go up as the rpm's go up. Probably something like 0-10V.
Thread Starter
Cruising
Joined: Jun 2019
Posts: 11
Likes: 0
From: Milton, WI
Thanks for the heads up on the scan tool... So I checked code on board and came up with 21 codes. I cleared them then drove it 4 more times for a distance. Now I have 8 and here they are:
10 PCM 3 codes:
P0522H
P0654HC
P0705H
99 HVAC 1 codes:
B0441HC
BO-RFA 4 codes:
U1096H
U1064H
U1016H
C2120H
Thanks for the help!!!
10 PCM 3 codes:
P0522H
P0654HC
P0705H
99 HVAC 1 codes:
B0441HC
BO-RFA 4 codes:
U1096H
U1064H
U1016H
C2120H
Thanks for the help!!!
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
P0654 = Engine Speed Output Circuit
Start checking the tach wire for bad connections.
Diagnostic Procedures
1. If IPC diagnostic system check was performed, go to next step. If IPC diagnostic system
check was not performed, go to INSTRUMENT PANEL CLUSTER DIAGNOSTIC
SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM. After performing IPC
diagnostic system check, go to next step.
2. With engine running, if vehicle tachometer indicates engine speed (RPM), see
DIAGNOSTIC AIDS . If no engine RPM is indicated, go to next step.
3. Turn ignition off. Locate and disconnect PCM connectors. See Fig. 7 . Install Signal
Generator Tester (J-33431-B) between ground and PCM connector C2 terminal No. 10
(White wire). See Fig. 8 . Turn ignition on. Turn tester on and set to generate a vehicle
speed signal. If tachometer indicates any RPM, go to next step. If tachometer does not
indicate any RPM, go to step 5 .
4. Check for poor connections at PCM connector. Repair as necessary. After repairs, go to
2001 Chevrolet Corvette
2001 ACCESSORIES & EQUIPMENT Analog Instrument Panels - Corvette
step 9 . If connections are okay, go to step 7 .
5. Check for open, short to ground or high resistance in White wire between PCM connector
C2 terminal No. 10 and IPC connector terminal A17. See Fig. 6 and Fig. 8 . White wire
passes through underhood fuse block at connector C1 terminal D4 and connector C2
terminal A3. See Fig. 9 and Fig. 10 . Repair as necessary. After repairs, go to step 9 . If
circuit is okay, go to next step.
6. Check for poor connections at IPC. Repair as necessary. After repairs, go to step 9 . If
connections are okay, go to step 8 .
7. Replace PCM. See POWERTRAIN CONTROL MODULE under REMOVAL &
INSTALLATION. After replacing PCM, go to step 9 .
8. Replace IPC. See INSTRUMENT PANEL CLUSTER under REMOVAL &
INSTALLATION. After repairs, go to next step.
9. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and allow it to
reach normal operating temperature. Operate vehicle within conditions for setting this DTC.
If DTC does not reset, system is okay. If DTC resets, go to step 2 .
Start checking the tach wire for bad connections.
Diagnostic Procedures
1. If IPC diagnostic system check was performed, go to next step. If IPC diagnostic system
check was not performed, go to INSTRUMENT PANEL CLUSTER DIAGNOSTIC
SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM. After performing IPC
diagnostic system check, go to next step.
2. With engine running, if vehicle tachometer indicates engine speed (RPM), see
DIAGNOSTIC AIDS . If no engine RPM is indicated, go to next step.
3. Turn ignition off. Locate and disconnect PCM connectors. See Fig. 7 . Install Signal
Generator Tester (J-33431-B) between ground and PCM connector C2 terminal No. 10
(White wire). See Fig. 8 . Turn ignition on. Turn tester on and set to generate a vehicle
speed signal. If tachometer indicates any RPM, go to next step. If tachometer does not
indicate any RPM, go to step 5 .
4. Check for poor connections at PCM connector. Repair as necessary. After repairs, go to
2001 Chevrolet Corvette
2001 ACCESSORIES & EQUIPMENT Analog Instrument Panels - Corvette
step 9 . If connections are okay, go to step 7 .
5. Check for open, short to ground or high resistance in White wire between PCM connector
C2 terminal No. 10 and IPC connector terminal A17. See Fig. 6 and Fig. 8 . White wire
passes through underhood fuse block at connector C1 terminal D4 and connector C2
terminal A3. See Fig. 9 and Fig. 10 . Repair as necessary. After repairs, go to step 9 . If
circuit is okay, go to next step.
6. Check for poor connections at IPC. Repair as necessary. After repairs, go to step 9 . If
connections are okay, go to step 8 .
7. Replace PCM. See POWERTRAIN CONTROL MODULE under REMOVAL &
INSTALLATION. After replacing PCM, go to step 9 .
8. Replace IPC. See INSTRUMENT PANEL CLUSTER under REMOVAL &
INSTALLATION. After repairs, go to next step.
9. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and allow it to
reach normal operating temperature. Operate vehicle within conditions for setting this DTC.
If DTC does not reset, system is okay. If DTC resets, go to step 2 .
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