another code-25 this time
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Joined: May 2004
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another code-25 this time
Many thanks to all who helped me out this weekend. I got alot done on the2.9. Now I have a new code to troubleshoot. After running the KOEO test and the KOER yesterday, I came up with a code 25 (knock not sensed during dynamic test). Today I replaced the k.s. and ran the KOER again and got the same thing. Am I doing something wrong or is my problem bigger than the knock sensor? This is on an 86 ranger , 2.9, 5-spd. base model pickup. Any ideas would be greatly appreciated. Thanks, Chris
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New User
Joined: May 2004
Posts: 11
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I think I erased the codes. I disconnected the neg. bat. terminal for a few minutes. The code reader says that a code 10 is an instruction to momentarily floor the accelerator to produce a knock. When I floored it, it knocked but was not sensed by whatever was supposed to sense it-thus the code 25. Is the computer or the module in the distributor supposed to sense the knock and how would I test that part? Thanks for any help you can offer. Chris
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
DTC 25 indicates that the Knock Sensor (KS) signal to the PCM was not sensed during the Dynamic Response Test in the Key On Engine Running Self-Test. Possible causes are:
- Damaged Knock Sensor.
- Open or short in harness.
- Damaged Powertrain Control Module (PCM).
- EEC Self-Test performed improperly.
However, if you haven't been experiencing any pinging (spark knock) from your engine, then I would not even worry about it.
Here's a sure-fire way of clearing the codes. When doing the EEC Self-Test, as soon as the fault codes begin to be displayed, de-activate the test by disconnecting the jumper wire or code reader.
- Damaged Knock Sensor.
- Open or short in harness.
- Damaged Powertrain Control Module (PCM).
- EEC Self-Test performed improperly.
However, if you haven't been experiencing any pinging (spark knock) from your engine, then I would not even worry about it.
Here's a sure-fire way of clearing the codes. When doing the EEC Self-Test, as soon as the fault codes begin to be displayed, de-activate the test by disconnecting the jumper wire or code reader.
Post Fiend
Joined: Dec 2001
Posts: 10,562
Likes: 4
From: South Jersey
If you still get the code try running these tests.
« DG -- Knock Sensor»
DG1 CHECK SENSOR VOLTAGE CYCLING
Possible Causes:
-- Damaged KS.
-- Open or short in harness.
-- Damaged PCM.
-- Altitude of 1830 meters (6,000 feet) or higher.
l Key off.
l Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires.
l Service as necessary.
l Install breakout box. Connect PCM.
l Key on.
l Read dc voltage between KS and SIG RTN at the breakout box.
l Is dc voltage reading between 2.4 and 2.6 volts?
Yes
GO to «DG2».
No
For DC voltage reading less than 2.4 volts:
GO to «DG4».
For DC voltage reading greater than 2.6 volts:
GO to «DG5».
DG2 CHECK FOR VOLTAGE INCREASE
l Key off.
l Breakout box installed, PCM connected.
l Start and run engine.
l Monitor voltage on the ac setting at idle and at 3,000 rpm between KS and SIG RTN at the breakout box.
l Does ac voltage reading increase?
Yes
RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
No
GO to «DG3».
DG3 CHECK RESISTANCE OF KS AND SIG RTN CIRCUITS
l Key off.
l Breakout box installed, PCM disconnected.
l KS disconnected (both KS on Mark VIII).
l Measure resistance between SIG RTN circuit at the KS vehicle harness connector and SIG RTN at the breakout box.
l Measure resistance between KS circuit at the KS vehicle harness connector and KS at the breakout box.
l Is each resistance less than 5.0 ohms?
Yes
GO to «DG4».
No
SERVICE open circuit. REMOVE breakout box. RECONNECT all components. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DG4 CHECK KS CIRCUIT FOR SHORT TO GROUND
l Key off.
l Breakout box installed, PCM disconnected.
l KS disconnected.
l Measure resistance between KS and PWR GDN at breakout box.
l Is each resistance greater than 10,000 ohms?
Yes
REPLACE KS. REMOVE breakout box. RECONNECT PCM. RECONNECT all components. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
No
SERVICE short circuit. REMOVE breakout box. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DG5 CHECK KS CIRCUIT FOR SHORT TO POWER
l Key off.
l Breakout box installed, PCM disconnected.
l KS disconnected (both KS on Mark VIll).
l Key on, engine off.
l Measure voltage between KS and PWR GND at breakout box.
l Is voltage less than 0.5 volt?
Yes
RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
No
SERVICE short circuit. REMOVE breakout box. RECONNECT all components. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
« DG -- Knock Sensor»
DG1 CHECK SENSOR VOLTAGE CYCLING
Possible Causes:
-- Damaged KS.
-- Open or short in harness.
-- Damaged PCM.
-- Altitude of 1830 meters (6,000 feet) or higher.
l Key off.
l Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires.
l Service as necessary.
l Install breakout box. Connect PCM.
l Key on.
l Read dc voltage between KS and SIG RTN at the breakout box.
l Is dc voltage reading between 2.4 and 2.6 volts?
Yes
GO to «DG2».
No
For DC voltage reading less than 2.4 volts:
GO to «DG4».
For DC voltage reading greater than 2.6 volts:
GO to «DG5».
DG2 CHECK FOR VOLTAGE INCREASE
l Key off.
l Breakout box installed, PCM connected.
l Start and run engine.
l Monitor voltage on the ac setting at idle and at 3,000 rpm between KS and SIG RTN at the breakout box.
l Does ac voltage reading increase?
Yes
RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
No
GO to «DG3».
DG3 CHECK RESISTANCE OF KS AND SIG RTN CIRCUITS
l Key off.
l Breakout box installed, PCM disconnected.
l KS disconnected (both KS on Mark VIII).
l Measure resistance between SIG RTN circuit at the KS vehicle harness connector and SIG RTN at the breakout box.
l Measure resistance between KS circuit at the KS vehicle harness connector and KS at the breakout box.
l Is each resistance less than 5.0 ohms?
Yes
GO to «DG4».
No
SERVICE open circuit. REMOVE breakout box. RECONNECT all components. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DG4 CHECK KS CIRCUIT FOR SHORT TO GROUND
l Key off.
l Breakout box installed, PCM disconnected.
l KS disconnected.
l Measure resistance between KS and PWR GDN at breakout box.
l Is each resistance greater than 10,000 ohms?
Yes
REPLACE KS. REMOVE breakout box. RECONNECT PCM. RECONNECT all components. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
No
SERVICE short circuit. REMOVE breakout box. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DG5 CHECK KS CIRCUIT FOR SHORT TO POWER
l Key off.
l Breakout box installed, PCM disconnected.
l KS disconnected (both KS on Mark VIll).
l Key on, engine off.
l Measure voltage between KS and PWR GND at breakout box.
l Is voltage less than 0.5 volt?
Yes
RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
No
SERVICE short circuit. REMOVE breakout box. RECONNECT all components. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
