Engine power loss, ECM unreadable

Tiny
HBSB2CARPROS
  • MEMBER
  • 2003 HONDA CIVIC
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 92,000 MILES
I have the car listed above EX model, four door sedan.

The check engine light is on, the immobilizer light is flashing, there is no communication with the scan tool. The tachometer is inoperative, the temperature gauge is inoperative. The car runs sluggishly, no acceleration, engine cuts out (bogs down) at higher rpm's greater than 3,400 (when tachomdeter was working).

DLC test:
With the key on or off and ECM's p31 unplugged from the ECM, and measuring voltage from dlc pin 5 (logic ground for ECM) to chassis ground, I get a nine volt reading. With ECM's p31 plugged into the ECM, (key on or off) and measuring voltage from dlc pin 5 to ground, the reading is zero volts. Why does this happen? Is this normal? How does the logic ground function in relationship to the ECM?
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Tuesday, January 18th, 2011 AT 4:58 AM

10 Replies

Tiny
MMPRINCE4000
  • EXPERT
I think Honda will have to fix this, the immobilizer is getting a bad resistance value from key, or a wiring problem exists.

Most of these systems will disable fuel and ignition and PCM.
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Friday, January 21st, 2011 AT 4:00 PM
Tiny
HBSB2CARPROS
  • MEMBER
I am stuck having to fix this problem myself because neither the Honda dealership and two other shops were unable to fix this. Definitely appears to be some kind of wire (electrical) problem. I am disappointed in the brevity of your response.
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Friday, January 21st, 2011 AT 4:12 PM
Tiny
MMPRINCE4000
  • EXPERT
Troubleshooting:
Turn the ignition switch ON (II) with a programmed key.
Check to see if the immobilizer indicator comes on.
Does the indicator come on?
YES - Go to step 3.
NO - Go to step 12.
Check the immobilizer indicator operation.
Does the indicator come on for 2 seconds, then go off?
YES - Go to step 4.
NO - Go to step 6.
Try to crank the engine.
Does the starter motor operate?
YES - Go to step 5.
NO - Check the starter motor.
Try to start the engine.
Does the engine start?
YES - If available, check the Status Log in the Immobilizer info with the HDS (see STATUS LOG ). If the Status Log is not available, the Immobilizer system is OK at this time.
NO - Do the symptom troubleshooting.
Check to see if the immobilizer indicator comes on and blinks.
Does the indicator blink?
YES - Go to step 24
NO - Go to step 7.
Disconnect the 7P connector from the immobilizer control unit-receiver.
Check to see if the immobilizer indicator goes off.
Does the indicator go off?
YES - Substitute a known-good immobilizer control unit-receiver and/or ECM/PCM.
NO - Go to step 9.
Turn the ignition switch OFF.
Remove the gauge assembly and disconnect its 22P (20P*) connector (see GAUGE ASSEMBLY REPLACEMENT )
Check for continuity between the immobilizer control unit-receiver 7P connector No. 5 (IMOARM) terminal and body ground.
Fig. 5: Checking Continuity Between Immobilizer Control Unit-Receiver 7P Connector (IMOARM) Terminal And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO, INC.
Is there continuity?
YES - Repair a short in the wire.
NO - Faulty immobilizer indicator, replace the gauge assembly.
Try to start the engine.
Does the engine start?
YES - Go to step 13.
NO - Go to step 18
Turn the ignition switch OFF.
Disconnect the 7P connector from the immobilizer control unit-receiver.
Check for voltage between the immobilizer control unit-receiver 7P connector No. 7 (+B) terminal and body ground.
Fig. 6: Checking Voltage Between Immobilizer Control Unit-Receiver 7P Connector (+B) Terminal And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO, INC.
Is there battery voltage?
YES - Go to step 16.
NO - Faulty No. 9 (10 A) fuse in the under-dash fuse/relay box. If the fuse is OK, check for an open in the wire between the immobilizer control unit-receiver and under-dash fuse/relay box.
Remove the gauge assembly, and disconnect gauge assembgly connector B (22P) connector (see GAUGE ASSEMBLY REPLACEMENT ).
Check for continuity between the immobilizer control unit-receiver 7P connector No. 5 (IMOARM) terminal and gauge assembly B (22P) connector No. 1 terminal.
Fig. 7: Checking Continuity Between Control Unit Terminal No. 5 & Gauge Assembly Terminal No. 1
Courtesy of AMERICAN HONDA MOTOR CO, INC.
Is there continuity?
YES - Faulty immobilizer indicator, replace the gauge assembly.
NO - Repair an open in the wire.
Turn the ignition switch OFF.
Disconnect the 7P connector from the immobilizer control unit-receiver.
Disconnect the ECM/PCM connector E (31P).
Attach the ECM/PCM connector E (31P) No. 7 terminal to body ground with a jumper wire.
Turn the ignition switch ON (II).
Check for voltage between the immobilizer control unit-receiver 7P connector No. 6 (IG1) terminal and body ground.
Fig. 8: Checking Voltage Between Immobilizer Control Unit-Receiver 7P Connector No. 6 (IG1) Terminal And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO, INC.
Is there battery voltage?
YES - Go to step 24.
NO - Faulty No. 4 (10A) fuse in the under-dash fuse/relay box. If the fuse is OK, check for an open in the wire between the immobilizer-control unit-receiver and under-dash fuse/relay box.
Turn the ignition switch OFF.
Check for continuity between the immobilizer control unit-receiver 7P connector No. 1 (LG3) terminal and body ground.
Fig. 9: Checking Continuity Between Immobilizer Control Unit-Receiver 7P Connector No. 1 (LG3) Terminal And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO, INC.
Is there continuity?
YES - Substitute a known-good immobilizer control unit-receiver and/or ECM/PCM.
NO - Repair an open in the wire. If the wire is OK, repair G101.
Turn the ignition switch OFF.
Connect the HDS to the data link connector.
Turn the ignition switch ON (II).
Monitor the System Check in the Immobilizer Info with the HDS.
Is the immobilizer system normal?
YES - Go back to step 1.
NO - Go to step 30.
Verify the System Check display on the HDS for the following information:
Harness short from the ECM/PCM to the immobilizer unit. (S-net line short)
The communication was not good between the ECM/PCM and the immobilizer unit by battery voltage low.
The communication was not good between the immobilizer unit and the ECM/PCM by influence of some noise.
Immobilizer unit failure
ECM/PCM failure
Does the HDS display any of the above information?
YES - Go to step 31.
NO - Go to step 35.
Turn the ignition switch OFF.
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Sunday, January 23rd, 2011 AT 2:19 PM
Tiny
HBSB2CARPROS
  • MEMBER
It was difficult trying to follow the test procedure above, could not find all the go to steps it would refer to. Is there a site I can get the original steps from?

I did find the TPS voltage at the ECM would not measure any higher than 1.7 volts. I get five volts at the TPS plug, and was able to measure 6k ohms of resistance on the TPS. I was also able to vary the throttle valve and notice the resistance vary on the TPS. I realize the TPS can still be non-linear and still be causing problems. Unfortunately, replacing it means replacing the entire throttle body valve! I was hoping for a more definitive test on the TPS before spending $300.00 or more for a throttle valve. The car does idle well, compression test was good. But, upon accelerating (opening the throttle valve by hand) the engine bogs down to almost shutting off mode.

I am open to more tips. I have learned a lot since beginning to troubleshoot the issues I am having with this car. Found out the wire diagram I got from mechanic (Mitchell's) did not totally match what I have in my car, so I am now stuck with using Alldatadiy. Unfortunately, their site does not give the wire schematic diagrams like the Mitchell one I had. Alldata's is more a block/function diagram. If I had an accurate wire diagram, I could easily follow out the wires, their color etc. Where can I get an accurate wire diagram of my car besides spending hundreds of dollars from the dealer?

I also tried calling Honda asking for an engineer and they would only defer me to their dealers. Been there, done that, to no avail.
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Sunday, January 30th, 2011 AT 12:07 AM
Tiny
MMPRINCE4000
  • EXPERT
Sorry for the cut and paste, but when we copy it and paste it, it loses the formatting.
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Friday, February 11th, 2011 AT 6:45 PM
Tiny
JM93635
  • MEMBER
To put it simple the ECM (or engine control module) is in limp mode. Get a new or used ECM and ignition with key coded and save time and trouble. Dealers will charge a substantial amount for this work and programming so check with some auto parts stores or eBay. Make sure the ECM and key ring ignition are paired. If you go through auto parts store write down VIN number, mileage and part number on the ECM. Hope this helps.
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Tuesday, May 31st, 2016 AT 3:13 PM
Tiny
MATTW_1999
  • MEMBER
Was this issue ever resolved? My car is having the exact same issue. I t is a 2002 Honda Civic two fdoor vetch. It starts runs sluggish especially upon acceleration. The green immobilizer light flashes all the time and the rpm, and temperature gauge's do not work. What do I do?
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Tuesday, August 15th, 2017 AT 2:58 PM
Tiny
KEN
  • ADMIN
Hello,

lets start by reading the codes to see what comes up.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please let us know what happens.

Cheers, Ken
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Wednesday, August 16th, 2017 AT 4:12 PM
Tiny
CHRIS PATRICK
  • MEMBER
I am having the same problem with my 2005 Honda Civic 1.7 To a T! Car will not scan and those gauges do not work and flashing key light. Did anyone figure this out? Help!
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Tuesday, June 5th, 2018 AT 11:04 AM
Tiny
KEN
  • ADMIN
Yes, I would try to do hard reboot of the system. Remove the negative battery cable and then hold it to he positive terminal for one minute this will discharge the capacitors and reboot the system. Here is a guide:

https://www.2carpros.com/articles/how-to-reset-a-security-system

Please let us know what happens.

Cheers, Ken
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Wednesday, June 6th, 2018 AT 9:58 AM

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